Chemistry Notes.18 19.1

GLOBAL ACADEMY OF TECHNOLOGY
IDEAL HOMES TOWNSHIP, RAJARAJESHWARINAGAR, OFF MYSORE ROAD,

BENGALURU – 560098. INDIA
DEPARTMENT OF CHEMISTRY
ENGINEERING
CHEMISTRY NOTES
SEMESTER: I / II SUBJECT CODE: 18CHE12/22
PREPARED BY
Dr. N SUMA , Dr. ASHOK S D ,Mr. ADARSHA J R ,Mr. BHASKAR M,

Mrs. ARATHI K & Dr RAVISHANKAR T N
FACULTY MEMBERS OF THE DEPARTMENT
VISION OF INSTITUTION
Become a premier institution imparting quality education in engineering and management
to meet the changing needs of society.
MISSION OF INSTITUTE
 Create environment conducive for continuous learning through quality teaching and
learning processes supported by modern infrastructure.
 Promote Research and Innovation through collaboration with industries.
 Inculcate ethical values and environmental consciousness through holistic education
programs.
DEPARTMENT OF SCIENCES AND HUMANITIES
VISION
To be an education provider in science and humanities with emphasis on excellence

in academic and research for the benefit of society.
MISSION
 Impart fundamental knowledge in science for understanding advancements in

engineering and technology.
 Provide students with linguistics competence in chosen language and improve
communication skill for personal and professional purposes.
 Develop intellectual atmosphere in science and humanities for professional
development.
 To inculcate human values and professional ethics among students for building
healthier society.
Subject Name Engineering Chemistry No. of Sessions 50

Subject Code 18CHE12/22 Year of Study 2018-19
COURSE OUTCOMES
CO. No. of Program
NO. Course Outcomes Bloom’s
Levels Sessions Outcom
es
On completion of this course, students are able to
Discuss the thermodynamic functions
CO1 and electrochemical energy systems Understand 10 PO1,PO2,
such as PO6,
electrodes and batteries.
Explain fundamental concepts of
CO2 corrosion, corrosion control and surface Understand 10 PO1,PO2,
modification methods namely PO6
electroplating and
electroless plating.
Describe the concepts of non renewable
CO3 (petroleum) and renewable (solar energy) Understand 10 PO1,PO2,
energy sources, calorific value of fuel and PO6,PO7
fuel cells.
Explain environmental pollution,
CO4 waste management and impurities in Understand 10 PO1,PO2,
water for PO6,PO7
production of potable water.
Illustrate different techniques of instrumental
CO5 methods of analysis and synthesis, properties Understand 10 PO1,PO2,
and applications of nanomaterials. PO6
Total Number of Sessions 50

Sub: Engineering Chemistry; Sem :I/II Prepared by: NS, SDA,JRA,BM,KA&TNR
PROGRAM OUTCOMES (POs)
Engineering Graduates will be able to:
1. Engineering knowledge: Apply the knowledge of mathematics, science, engineering
fundamentals, and an engineering specialization to the solution of complex engineering
problems.
2. Problem analysis: Identify, formulate, review research literature, and analyze complex
engineering problems reaching substantiated conclusions using first principles of mathematics,
natural sciences, and engineering sciences.
3. Design/development of solutions: Design solutions for complex engineering problems and

design system components or processes that meet the specified needs with appropriate
consideration for the public health and safety, and the cultural, societal, and environmental
considerations.
4. Conduct investigations of complex problems: Use research-based knowledge and research

methods including design of experiments, analysis and interpretation of data, and synthesis of
the information to provide valid conclusions.
5. Modern tool usage: Create, select, and apply appropriate techniques, resources, and modern
engineering and IT tools including prediction and modeling to complex engineering activities
with an understanding of the limitations.
6. The engineer and society: Apply reasoning informed by the contextual knowledge to assess
societal, health, safety, legal and cultural issues and the consequent responsibilities relevant to
the professional engineering practice.
7. Environment and sustainability: Understand the impact of the professional engineering

solutions in societal and environmental contexts, and demonstrate the knowledge of, and need
for sustainable development.
8. Ethics: Apply ethical principles and commit to professional ethics and responsibilities and
norms of the engineering practice.
9. Individual and team work: Function effectively as an individual, and as a member or leader in
diverse teams, and in multidisciplinary settings.
10. Communication: Communicate effectively on complex engineering activities with the

engineering community and with society at large, such as, being able to comprehend and write
effective reports and design documentation, make effective presentations, and give and receive
clear instructions.
11. Project management and finance: Demonstrate knowledge and understanding of the
engineering and management principles and apply these to one’s own work, as a member and
leader in a team, to manage projects and in multidisciplinary environments.
12.Life-long learning: Recognize the need for, and have the preparation and ability to engage
in independent and life-long learning in the broadest context of technological change.
Global Academy of Technology, RR nagar , Bengaluru 4

MODULE-1
ELECTROCHEMISTRY AND ENERGY STORAGE SYSTEM
(CO1)
Electrochemistry:Use of free energy in chemical equilibria: Thermodynamic functions:
Definitions of free energy and entropy. Cell potential, derivation of Nernst equation for
single electrode potential, numerical problems on E,E0 and Ecell. Reference electrodes:
Introduction; Construction, working and applications of calomel electrodes. Ion selective
electrode – Definition, construction and working of glass electrode, determination of pH
using glass electrode. Concentration cells: Electrolyte concentration cell, numerical
problems.
Energy storage systems: Introduction, classification-primary, secondary and reserve
batteries. Construction ,working and applications of Ni-MH and Li-ion batteries.
ELECTROCHEMISTRY
Introduction:
Electrochemistry is the branch of chemistry concerned with electrolysis and other similar
phenomenon occurring, when a current is passed through an electrolyte or concerned with
the behaviour of ions in solutions and the properties shown by these solutions. An important
aspect of electrochemistry is the inter conversion of electrical energy and chemical energy
that takes place through oxidation-reduction (Redox) reactions.
Electrolyte is a chemical or its solution in water, which conducts current through ionization.
Electrolysis is a chemical change, generally decomposition effected by a flow of current
through a solution of the chemical or its molten state, based on ionization.
Electrochemical cells: -
An electro chemical cell is a device which converts chemical energy into electrical
energy or electrical energy into chemical energy. Electrochemical cells are of two types:
galvanic cell and electrolytic cell.
Galvanic cell: A galvanic cell is an electrochemical cell in which chemical energy is
converted into electrical energy. Example: Daniel cell
Electrolytic cell: Electrolytic cell is a type of electrochemical cell in which electrical energy
is converted into chemical energy.
Electromotive force (E.M.F.):-
The potential difference between two electrodes of a galvanic cell which causes the flow
of current from one electrode (higher potential) to the other (lower potential) is called the
E.M.F.
Ecell=Ecathode - E anode
E0cell=E0cathode - E0anode

Thermodynamic functions:
Entropy: It is the measure of disorderness or randomness of a system.The entropy change

during a process is mathematically defined as S=q/T,where q is the heat exchanged during
the process. It is expressed in terms of joules per degree Kelvin (J/K).This is known as
entropy unit. Entropy is an extensive property, depends upon the amount of the substance
present.
Free Energy: The spontaneity of a process cannot be predicted on the basis of enthalpy and
entropy. For this purpose a new function called Gibbs free energy is defined. Gibbs Free
energy of a system is defined as the maximum amount of energy available to a system to
performwork. Gibbs free energy is denoted by the symbol G .
Single Electrode Potential

The potential developed at the interface between the metal and the solution where the metal
is in contact with its own ions.
Derivation of Nernst’s equation:-
The Nernst’s equation is used in determining of the single electrode potential as well as
E.M.F of the given cell.
Consider a redox reaction
Mn+ + ne- ↔ M
According to thermodynamics , the decrease in free energy (-∆G) represents the maximum
amount of work
-∆G = Wmax
Wmax= nFE
The change in free energy for the above redox reaction is given by,
∆G = -nFE --------------- (1)
Under standard conditions, when the concentrations of all species is unity, the standard free
energy change is given by the equation
∆G0 = -nFE0 ----------- (2)
The equilibrium constant K is related to change in free energy change by the Vant Hoff
equation
∆G =∆G0+ RTlnK ------------- (3)

Applying law of mass action to above redox reaction
Where K= [M]/[Mn+]
Substitute the value of K in equation (3)

∆G =∆G0+ RT ln [M]/[Mn+]
∆G =∆G0+ RT ln [M]- RT ln[Mn+]
Substitute from equ (1) and (2) for ∆G and ∆G0
-nFE = -nFE0+ RT ln [M]- RT ln[Mn+]
Divide throughout by -nF

-nFE = -nFE0+ RT ln [M]- RT ln[Mn+]
-nF -nF -nF -nF
Under standard conditions M=1, hence the above equation becomes (

since ln(1)=0 )
E = E0 + RT ln[Mn+]
nF
Substituting the values of R = 8.314 JK-1mol-1, F = 96,500 C mol-1, T = 250C.

Converting ln to log base10. The above equation reduces to,
E = E0 + 0.0591 log [Mn+]

n
Reference Electrodes :- Reference electrodes are electrodes whose potentials are known
and are used for the determination of potentials of other electrode. Reference electrodes are
of two types
1. Primary reference electrodes: Example- Standard hydrogen electrode (SHE)
2. Secondary reference electrodes : Examples – Calomel electrode, Silver-Silver
chloride electrode
Calomel electrode:-
 Calomel electrode is a metal-metal salt ion electrode and is a secondary reference
electrode.
 Calomel electrode consists of mercury, mercurous chloride and KCl solution.
 Mercury is placed at the bottom of the glass tube and it is covered with a paste of
mercurous chloride with mercury.
 A glass tube is filled with KCl solution of known concentration (saturated, 1N or 0.1N)
through the side tube .
 A platinum wire sealed into a glass tube is dipped into mercury and used to provide the
external electrical contact.
 Depending on the concentration of the KCl used calomel electrode develops potential. If
saturated KCl solution is used it develops a potential of 0.2422V. The electrode is
reversible with chloride ions.

The cell is represented as Hg / Hg2Cl2 / Cl-
The calomel electrode can acts as anode or cathode depending on the nature of the other
electrode of the cell.
 When it acts as anode:2Hg + 2Cl Hg2Cl2 + 2e-
 When it acts as cathode :Hg2Cl2 + 2e-
2Hg + 2Cl- Equilibrium reaction: Hg2Cl2 + 2e- ↔ 2Hg
+ 2Cl-
The electrode potential is given by,

E = E0 – 0.0591 log [Cl-] at 298 K
Advantages of Calomel elctrode:

1. It has simple construction
2. Cell potential is constant over a longer period
3. The cell potential does not vary with temperature
4. The cell potential is reproducible.
Applications of Calomel electrode:
1. Calomel electrode is used as secondary reference electrode in the measurement of
electrode potential.
2. It is most commonly used as reference electrode in all potentiometric & pH
determinations.
Ion selective electrode: Ion selective electrode is the one which selectively responds to a
specific ion in a mixture and the potential developed at the electrode is a function of the
concentration of that ion in the solution.
Example: a) glass electrode (exchanges H+ ions with the solution)
b) LaF3 electrode for fluoride determination

Glass Electrode:-
 Glass electrode is a pH sensitive electrode, most widely used for pH determination.
 The glass electrode consists of a glass bulb made up of special type of glass (corning
glass) with high electrical conductance.
 The glass bulb is filled with 0.1M HCl and is inserted with a Ag-AgCl electrode, which is
the internal reference electrode and also serves for the external electrical contact.
 The electrode is dipped in a solution containing H+ ions.
 The glass electrode can be represented as Ag / AgCl / 0.1M HCl / glass
When dipped in a solution it can be represented as

External analyte solution
[H+] = C1 0.1M HCl Ag / AgCl
C2 = 0.1 (internal reference electrode)
E1 E2
The exchange of ions by the inner and outer membrane gives rise to a boundary potential.
This boundary potential consists of two potentials E 1 and E2 which are associated with the
outer and inner membranes respectively.
Eb = E1 – E2
The potential of the glass electrode is given by
EG = E0G + 0.0591 log (H+)
Determination of pH by using glass electrode:-

In this experiment glass electrode is combined with calomel electrode. Glass electrode acts
as indicator electrode and calomel acts reference electrode. Both the electrodes are
connected to a PH meter and both the electrodes are dipped into the given unknown PH
solution.

The cell assembly is represented as

Hg/Hg2Cl2/Cl-//solution of unknown PH/ glass/ HCl(0.1M)/AgCl/Ag
The PH is determined by using following relation,
Ecell = EGlass - Ecalomel .............. (1)

For glass electrode,
EGlass = GE 0 + 0.0591 log[H+] {-log[H+] = pH}
0
EGlass =EG G - 0.0591pH ............. (2)
Substituting (2) in (1)
Ecell = E0G –0.0591pH- Ecalomel
pH = E0G –Ecalomel -Ecell

0.0591
Concentration Cell
Concentration cells are the galvanic cells consisting of anode and cathode made up of
similar metals dipped in its electrolyte solution containing its own ions of different
concentrations. The electrode which is in contact with higher electrolyte concentration acts
as cathode and the one with lower electrolyte concentration acts as anode.
The emf of the concentration cells is given by the Nernst equation,
E = 0.0591 log [C2 ]

n [ C1]
Where C2> C1
Ex:- Zinc concentration cell:-

It consists of anode and cathode made up zinc dipped in zinc sulphate solution of different
concentrations. Both the half cell is internally connected by means of salt bridge and
externally by a wire through an ammeter.
Cell reactions:
Anode: Zn → Zn2+ (C1)+ 2e-
Cathode: Zn2+ (C2) + 2e- → Zn
Cell can be represented as Zn/Zn2+ (C1) // Zn2+ (C2)/Zn
Numerical Problems:- ( Concentration cell)

1. A concentration cell is constructed by dipping copper rods in 0.001M and 0.1M CuSO4
solutions. Calculate the emf of the cell at 298K.
At the anode, Cu → Cu2+ + 2e-
At Cathode Cu2+ + 2e- → Cu
E = 0.0591/n log [C2 / C1]

= 0.0591/2 log [0.1/0.001] E
= 0.0591 V
2.The spontaneous galvanic cell tin|tin ion (0.024M)||tin ion(0.064M)|tin develops a

potential of 0.0126 V at 250C. Calculate the valency of tin.
Ans:
Ecell= 0.0591/n log[C2]/[ C1]

n = 0.0591/Ecell log [C2]/[ C1]
= 0.0591/0.0126 log[ 0.064/0.024] n
= 1.998 = 2
3.Two copper rods placed in copper sulphate solutions to form a concentration

cell.Calculate the cell potential if one of the solutions is diluted to 1/5 th of its original
concentration.

Ans:
Assume C2 = 1M then C1 = 1/5 C2
Ecell = 0.0591/n log[C2]/[ C1]

= 0.0591/2 log[1]/[1/5]
= 0.0591/2 log 5
= 0.0206 V
4. The emf of the cell Cu/CuSO4(0.01M)//CuSO4(xM)/Cu is 0.0295V at 25°C.Find the

value of x.
Ans: Ecell = 0.0591/n log[C2]/[ C1]
0.0295= 0.0591/2 log x/0.01
0.0295 =0.0295 log x/0.01
1= log x – log 0.01
1= logx-(-2) x
= 0.1M
Numerical :- (Electrode Potential using Nernst equation)
1. Iron rod is immersed in 1.0M FeSO4 and Mn rod is immersed in 0.1M MnSO4 .
Calculate the voltage generated by coupling these two electrodes given standard reduction
potential of Fe and Mn are -0.40V and -1.18V respectively.
At the anode, Mn → Mn2+ + 2e-
At Cathode Fe2+ + 2e- → Fe
Fe2+ +Mn→ Mn2+ +Fe
Cell representation :- Mn/MnSO4(0.1M)//FeSO4(1M)/Fe
E = E0 + 0.0591 log [Cathodic species]

n [Anodic Species]
Eo=Ecathode - Eanode
= -0.40 –(-1.18) =0.78V

E= 0.78 + 0.0591 log [1M]
2 [0.1M]
= 0.78+0.02955
E = 0.8095V
2] A cell is constructed by coupling a zinc electrode dipped in 0.5M ZnSO4 and nickel
electrode dipped in 0.05M NiSO4. Write the cell representation, cell reaction. Calculate
EMF of the cell, Given that standard reduction potential of Zn and Ni is -0.76V &
-0.25, respectively.
Cell representation :- Zn/ZnSO4(0.5M)//NiSO4(0.05M)/Ni

At the anode, Zn → Zn2+ + 2e-
At Cathode Ni2+ + 2e- ---> Ni
Ni2+ +Zn→ Zn2+ +Ni
E = E0 + 0.0591 log [Cathodic species] n

[Anodic Species]
Eo=Ecathode - Eanode
= -0.25-(-0.76) = +0.51V
E= 0.51 + 0.0591 log [0.5M]

2 [0.05M]
= 0.51+0.0295
E= 0.539V
3] Write the electrode reaction and calculate the EMF of the following cell at 298K.Given
E0=0.46V and cell representation is Cu/Cu+2(1x10-2M)//Ag+(1x10-1M)/Ag and calculate
the free energy change for one mole of Ag + ion.
At the anode, Cu→ Cu2+ + 2e-
At Cathode , (Ag1+ + e- → Ag) x2
2Ag1+ +Cu → Cu2+ +2Ag

n [Anodic Species]
=0.46+ 0.0591 log [Ag+]2

2 [Cu2+]
=0.46+ 0.0591 log [1X10-1]2
2 [1X10-2]
E=0.46V
∆G= - nEF = -2 x 0.46 x 96500 = -887KJ
For 2 moles of Ag+ ions --- -887

For 1 mole of Ag+ ions--- 443 KJ/Mol.
4] Calculate the potential of an Ag-Zn cell at 298K, if the concentration of Ag+ and Zn2+
are 5.2x10-6M and 1.3x10-3M respectively. E0 of the cell at 298K is 1.56V.Calculate the
change in free energy.
At the anode, Zn→ Zn2+ + 2e-
At Cathode , (Ag1+ + e- → Ag) x2

2Ag1+ +Zn → Zn2+ +2Ag

n [Anodic Species]
= 1.56 + 0.0591 log [Ag+]2

2 [Zn2+]
= 1.56+ 0.0591 log [5.2X10-6 ]2
2 [1.3X10-3 ]
E= 1.33V
∆G = -nFE
= - 2 x 96500 x 1.33 = - 256 KJ
5] Calculate the reduction potential of Cu when it is in contact with 0.5M CuSO 4 solution
at 298K. The E0 value of Cu is 0.34V.
E = E0 + 0.0591 log [Mn+]
n
E = 0.34 + 0.0591 log [Cu2+]
2
=0.34 + 0.02955 log[0.5] E
= 0.33v
Energy Storage systems
Introduction:
A battery is a compact device consisting of a number of galvanic cells that can generate
electric power and can acts as a portable source of electrical energy. It stores chemical
energy in the form of active materials and on demand converts it into electrical energy
through redox reactions. Battery are widely used in calculators , watches, hearing aids ,
pace makers, computers, automobile engines, electroplating industrials, military and space
application and standby power supply in the form of inventors.
The size of battery can range from a fraction of cm3 to several dm3. Batteries have
revolutionized the telecommunication systems and also being used as an alternative to
conventional fuels (petrol, diesel, LPG etc.) in automobile industry.
Classifications of battery:-
Batteries are classified into three types
1) Primary batteries: - These are the batteries in which the cell reactions are irreversible.
Hence such batteries are not rechargeable. Such batteries are called as primary batteries. Ex;
- Dry cell.
2) Secondary batteries:- These are the batteries in which cell reactions are reversible.
They are also called as storage batteries. Hence such batteries can be recharged for number
of times. Ex:- Lead storage battery, nickel- cadmium battery etc.

3) Reserve batteries:- The batteries which can be stored in an inactive state and made
ready for use by activating them prior to the applications (usage) are called as reserved
batteries. The key components of the batteries such as electrolyte and electrode is separated
from the battery. And the battery is stored for a longer time. The electrolyte if filled before
its usage. The advantages of the reserved batteries are,
Batteries can be stored for a longer period.
• To prevent corrosion at contact points during storage.
• Self-discharging reactions during storage can be eliminated or avoided
• They can be used whenever they are required.
Ex: Mg-water activated batteries, Zn-Ag2O batteries etc
Nickel-metal hydride (Ni-MH) battery:-
 Anode: Nickel grid coated with metal hydrides such as ZrH2, VH2 and TiH2 with
hydrogen storage metal alloy such as LaNi5 or Ti-Ni.
 Cathode: Porous nickel grid coated with nickel oxy hydroxide.
 Electrolyte: Aqueous KOH solution.
 Separator : Polypropylene
 This cell develops a potential of 1.35V
 Cell representation : MH2/ KOH/ Ni(OH)2, NiO(OH)
Discharge reaction:
Anode: MH2 +2OH- → M + 2H2O + 2e-
Cathode: 2NiO(OH) + 2H2O + e- → 2Ni(OH)2 + 2OH-

MH2 + 2NiO (OH) → M + 2Ni(OH)2
During charging the above reactions is reversed.

Applications:-

1) It is used in cellular phones, computers etc.
2) It is used in electric vehicles.
Advantages:
 High capacity
 Sealed construction, no maintenance required
 Cadmium free-minimal environmental problems.
 Rapid recharge capability
 Long cycle life and long shelf life.
Lithium Batteries:-
Lithium is a light metal with low electrode potential and good conductivity. Lithium
is good material for batteries and can be expected to have high potential and high energy
density. The batteries where lithium is used as an anode are known as lithium batteries. A
large number of lithium batteries are available which have lithium as anode, but they differ
in choice of cathode and electrolyte. Lithium batteries may be classified as primary and
secondary. Primary batteries are not chargeable and involve Li metal whereas secondary
batteries are chargeable and involve lithium ion .
Li- ion battery

The Li – ion battery is rechargeable battery best suited to mobile devices that
require small size, light weight and high performance.
 Anode: Lithium intercalatable graphite
 Cathode: Lithium metal oxides (Li-MO2)
 Electolyte :Lithium salt such as LiPF6 dissolved in organic solvents like propylene
carbonate, ethylene carbonate etc.
 Separator: Microporous polypropylene or polyethylene
 Li ion battery develops a potential of 3.6V

Cell reactions:
Anode : LiC6 ↔ Li+ + 6C + e-
Cathode: +
MO2 + Li + e-↔ Li - MO2
Li - C6 +MO2 ↔ Li-MO2 + 6C
Uses: Used in cell phone, note PC, portable LCD Tv, portable CD player, semiconductor
driven audio etc.
Assignment questions:
1. Define single electrode potential. Derive an expression for electrode potential.

2. Define reference electrodes? Explain construction & working of calomel electrode.
3. Define Ion selective electrodes? Explain the construction and working of glass
electrode.
4. Explain the determination of PH using glass electrode.
5. Describe the concentrations cells? Explain with an example.
6. The spontaneous galvanic cell tin/tin ion (0.034M) // tin ion (0.074) / tin, develops a
Potential of 0.0136 V at 250C. Calculate the valency of tin.

7. Calculate the emf of the following concentration cell at 298K.
Ag(s) / Ag+(0.01) // Ag+(0.5) / Ag(s) (Ans.0.101 V)

8. A concentration cell was constructed by immersing two silver electrodes in 0.05 M and
0.1 M AgNO3 solution . Write cell representation, cell reaction and calculate the emf
of concentration cell.
9. The emf of the cell Ag/ AgCl(0.0083M) //AgNO3 (xM)/Ag was found to be 0.074V.
Calculate the value of x and write cell reaction.
10. An electrochemical cell is constructed by immersing a silver wire in AgNO 3 solution of
0.5M and a Cadmium wire in CdSO4 solution of 0.25 M at 250C. Write the cell
representation, cell reaction and calculate emf of the cell and change in free energy.
Given E0 Ag+ = 0.8 V and E0 Cd 2+ = -0.40V, F= 96.5 KJ/Kg/V
11. Calculate the potential of cell formed from Ag+/Ag and Cu / Cu2+ electrodes if
concentration of Ag+ and Cu2+ are 4.2 x 10-6 M and 1.3 x 10-3M respectively.(
Given E0cell = 0.46V ). Calculate free energy change for reduction of one mole of
Ag+ by Cu.
12. Explain the construction ,working and applications of Ni-MH battery and Lithium ion
battery

MODULE-2
CORROSION AND METAL FINISHING
(CO 2)
Corrosion: Introduction, Electrochemical theory of corrosion, Factors affecting the rate of
corrosion: ratio of anodic and cathodic areas, nature of metal, nature of corrosion product, nature
of medium –pH, conductivity and temperature. Types of corrosion- Differential metal corrosion,
Differential aeration corrosion (Pitting and water line corrosion).Corrosion control: Inorganic
coatings – Anodizing of Al,Metal coatings – Galvanization, Cathodic protection -Sacrificial anodic
and impressed current methods.
Metal Finishing: Introduction, Technological importance. Electroplating: Introduction, principle

governing- Polarization, decomposition potential and overvoltage. Electroplating of chromium
(decorative and Hard). Electroless plating : Introduction, Electrolessplating of nickel and copper,
distinction between electroplating and electroless plating process.
Introduction: Corrosion is a process of destruction or deterioration of metal by the environment

through chemical or electrochemical reactions.
Most of the metals and alloys undergo corrosion except the noble metals. Corrosion is like
“Cancer”for the metals.
Eg: Rusting of Iron- it is due to formation of hydrated ferric oxide.
Types of corrosion:
1. Dry Corrosion: Corrosion taking place in the absence of moisture that is direct chemical reaction
taking place between metal and dry gases.
2. Wet Corrosion: Corrosion taking place in the presence of moisture or aqueous wet environment.
Electrochemical Theory of Corrosion:

According to electrochemical theory, corrosion of metal takes place due to the formation of
anodic and cathodic regions on the same metal surface or when two different metals are in contact
with each other in the presence of a conducting medium.
 When a metal is exposed to aqueous environment it divides metal into two parts as anode and
cathode on same metal surface.
 At anodic region oxidation takes place where e- are liberated. Corrosion takes place at the
anode.
 Cathodic region is protected as it undergoes reduction where it consumes or accepts liberated
e-.
 Anodic and cathodic reactions are going to take place due to metal impurities in bulk amount
and difference in oxygen concentration on metal surface.

Corrosion reactions:
Anodic reaction: Oxidation of metal takes place where metal converts to metal ion.
M ------ Mn+ + ne-
Fe Fe2+ + 2e-
Cathodic reaction: Two types of reaction going to take place
1. Liberation of hydrogen: In absence of oxygen

i) In acidic medium cathodic reaction is
2H+ +2e- H2
ii) In neutral or alkaline medium, hydroxide ions are formed.

2H2O + 2e- 2OH- + H2
2. Absorption of Oxygen:
i) In acidic medium water is formed
4H+ +2e- +O2 2H2O
ii) Alkaline medium

2H2O + O2 +4e- 4OH-
This water accepts electrons to form OH- ions. Fe2+ ions and OH- ions defuse towards each other and
forms corrosion product (Ferrous hydroxide).
Fe2+ + 2OH- Fe(OH)2 (insoluble)
This Ferric hydroxide further undergo oxidation in presence of oxygen to form Rust
Fe(OH)2 + H2O + ½ O2 (Fe2O3. 3H2O) Rust

FACTIORS AFFECTING THE RATE OF CORROSION
1. Ratio of anodic and cathodic areas. The rate of corrosion depends on the size of anodic and
cathodic area. If metal forms small anodic region and larger cathodic region then corrosion is
faster and intensive at anodic region.
At anode oxidation takes place and electrons are liberated. At cathode electrons are consumed.
When anode area is smaller electrons liberated at anode is rapidly consumed at larger cathodic area.
This process makes anodic reaction to take place at maximum rate of corrosion. If cathode area is
smaller than anode area consumption of electrons will be slower and rate of corrosion decrease.
Eg: Broken coating of Tin (larger cathodic area) on iron surface (smaller anodic area)
Zinc plating on Iron gives smaller cathodic region and larger anodic region. If zinc plating peels of at
same point still rapid corrosion does not occur due to smaller cathodic area and larger anodic area.
2. Nature of Metal: Metals with lower electrode potential values are more reactive than the metals with
higher electrode potential. Hence more reactive metals are more susceptible for corrosion. The
tendency of a metal to undergo corrosion decreases with increase in electron potential.
Eg: Metals like Sodium, Zinc, Magnesium have low electrode potential values and hence susceptible for
corrosion.
Noble metals like gold, platinum have higher electrode potential value less susceptible for corrosion
3.Nature of corrosion product: When corrosion product deposited is insoluble, stable uniform and
non-porous, it acts like barrier between the metal and corrosion atmosphere, which prevents further
corrosion. On other hand if corrosion product is soluble, unstable non-uniform and porous, rate of
corrosion is fast and continuous
Eg: Aluminium, Titanium and chromium form a protective film of metal oxide on surface and prevents
further corrosion where as in Zinc, Iron and Magnesium corrosion product formed do not form
protective film and corrosion continuous.
4. pH of the medium: In general lower pH of corrosion medium, higher is the corrosion rate. But

exception case is Al, Zn shows faster corrosion in alkaline medium. In case of Iron rate of corrosion
will be less at greater pH because of the formation of protective coating of hydrous oxides of iron.
5.Conductivity of medium: As the conductivity of the corrosion medium increases, the corrosion rate
also increases. Higher the conductivity of medium , faster the ions can migrate between the anodic
and cathodic regions of the corrosion cell. This facilitate higher corrosion rate.
6. Temperature: In general rate of chemical reaction increases with increase in temperature. Corrosion
is one such chemical reaction. Higher the temperature, higher is the ionic conductivity in corrosion
medium and higher is the corrosion rate.
Types of corrosion
Differential Metal Corrosion (galvanic corrosion):
Differential metal corrosion occurs when two dissimilar metals are in contact with each other and
expose to corrosive environment. The two metals differ in their electrode potential. The metal with
lower electrode potential acts as anode, the metal with higher electrode potential acts as cathode. The
potential difference between two metals is a driving force for corrosion. Here anode undergoes
corrosion.
Eg: When iron is in contact with copper.
Fe++ 2OH-
-
F e Cu
e
ANODE CATHOD
E
Fe has lower electrode potential when compared to copper. Hence iron undergo oxidation and get
corroded.
Reactions:
At anode:
Fe Fe2+ + 2e-
At cathode:
H2O + ½ O2 + 2e- 2OH-
Overall Reaction
Fe(OH)2 + H2O +½ O2 (Fe2O3. 3H2O) Rust
Other examples
1. Steel screws in copper sheet
2. Steel screws with copper washer

3. Nut and bolts made of different metals.
Differential aeration corrosion:
Differential aeration corrosion occurs when a metal surface is exposed different oxygen
concentration. Part of metal exposed to higher oxygen concentration acts as cathode and metal
exposed to lower oxygen concentration acts as anode. The anodic region undergoes oxidation and
gets corroded.
Eg: When iron rod partially dipped in water.
Reaction:
At anode:
Fe Fe2+ + 2e-
At cathode:
H2O + ½ O2 + 2e- 2OH-
Overall Reaction
Other examples
a) Part of nail inside the wall undergoes corrosion.
b) Partially buried pipeline in soil undergoes corrosion.
c) Partially filled iron tank undergoes corrosion inside water.
This differential aeration corrosion is divided in to two types
Water line corrosion

This is due to differential oxygen concentration
Eg: Water storage tank
Poor oxygenated more oxygenated

Area (anode) area (cathode)
When a steel tank partially filled with water for a long time, the inner portion of the tank below the
water line is exposed only to dissolved oxygen whereas the portion above waterline is exposed to
more oxygen. Thus the portion below the water acts as anode and undergoes corrosion. The upper
portion acts as cathode and it is unaffected.

At anode:
Fe Fe2+ + 2e-
At cathode:
H2O + ½ O2 + 2e- 2OH-
Overall Reaction
Fe(OH)2 + H2O +½ O2 (Fe2O3.3H2O) Rust
Pitting Corrosion
Corrosion product
More oxygenated cathode
Anode
Iron metal
When a small dust particle gets deposited on metal surface, region below the dust particle is exposed
to less oxygen when compared to remaining part of the metal. Therefore region below dust particle
acts as anode and undergoes corrosion and forms a pit. Here formation of small anodic area and
large cathodic area results in intense corrosion below the dust particle.
Reaction:
At anode:
Fe Fe2+ + 2e-
At cathode:
H2O + ½ O2 + 2e- 2OH-
Overall Reaction
Corrosion Control: Corrosion can be controlled by protecting the surface of the metal or by
preventing the formation of galvanic cells.
Protective Coatings: Application of protective coating is one of the important methods of corrosion
control. The protective coating protects the metal from corrosion by acting as a barrier between the
metal and the corrosion environment. The principle types of coatings applied on the metal surface
are
a) Metal coating b) Inorganic coating c) Organic coating
a) Metal coating : The process of covering base metal with a layer of protective metal is known as

metal coating. They are divided into two types,
i) Anodic coatings: It is produced by coating a metal surface with more active metals which acts as
anodic to base metal.
Eg: Galvanization
Galvanization is a process of coating base metal like iron or its alloy surface with anodic and active
Zn metal. One of the important characteristic of anodic coating is even if coating is ruptured base
metal does not undergo corrosion because base metal exposed to environment will be cathodic in
nature with respect to coating metal.
Galvanization process involves following steps:
 Metal surface is washed with organic solvents to remove organic matter.
 Rust and other deposits removed by washing with hot dil H2SO4 is called pickling
process.
 Then it is well washed with water.
 It is air dried by passing hot air.
 Then it is dipped in molten zinc, maintained at 430-4500C and covered with flux of
ammonium chloride and zinc chloride to increase adhesion property.
 Excess of zinc on surface is removed by passing a pair of hot rollers, which removes
excess of zinc and produces thin coating.
Application: Galvanized materials are used in fencing wire, buckets, bolts, nuts, nails, screw etc.
Inorganic coating: It is chemical conversion coatings where metal surface is converted to a

compound by chemical or electrochemical process which forms barrier. There are two types
a) Anodizing (Anodizing of aluminium)

It is a electrochemical process which forms protective passive (non reactive) oxide film on metal
surface.
Here aluminium metal is made as anode in a suitable oxidizing electrolyte like sulphuric acid, chromic
acid, oxalic acid bath at a temperature of 30 - 400 C and moderate current density. A thin film of
Al2O3 is deposited on surface, this acts as protective layer preventing the corrosion. This film tend to
be porous and provides good adherence for paint and dyes.
Uses: It is used as soap boxes, tiffin boxes, window frames etc. Anodic films are also used for number of

cosmetic effects.
Cathodic protection: It is a method of protecting a metal or alloy from corrosion by converting

metal completely into cathodic and no part of the metal is allowed to act as anode.
There are two types,
a) Sacrifical anodic method:
 Protected metal structure is converted to cathode by connecting to more active metal

 This active metal acts as anode Eg: Mg,Al,Zn etc
 This active metals undergo preferential corrosion, protecting the metal structure
 Since the anodic metals are sacrificed to protect the metal structure, hence the name.
 Exhausted sacrificial anodes are replaced when required.
Eg: Mg block connected to buried pipe tank in water

Mg block connected to underground oil storage tank.
b) Impressed current method:
 Applying direct current larger than the corrosion current

 Protected metal is made cathodic by connecting it to cathode of external source of current
 Anode of electric source is connected to inert electrode(anode)
 Metal structure being cathode does not undergo corrosion.
 Anode being inert remains unaffected
Eg: Platinum, graphite, silicon, iron are used as anodes

Assignment Questions:
1. Explain electrochemical theory of corrosion taking iron as an example.

2. Describe differential metal corrosion
3. Explain differential aeration corrosion
4. Describe pitting corrosion
5. Explain waterline corrosion
6. Explain the factors affecting rate of corrosion.
7. Define anodizing? Explain anodizing of aluminium
8. Explain the process of galvanization
9. Define cathodic protection? Explain sacrificial anode and impressed current method.
METAL FINISHING
Definition: Metal finishing is the process carried out to modify the surface properties of a metal by
electro deposition of a thin layer of noble metal on base metal.
Technological importance of metal finishing:
1. To increase the corrosion resistance
2. To increase in the Wear and tear resistance
3. To increase the Thermal and Electrical resistance
4. To impart Hardness of the surface.
5. Thermal and Optical reflectivity. (e.g., brightness or color)
6. To increase the Solderability
7. In the manufacture of printed circuit board etc.
Important techniques of metal finishing are: 1.Electroplating. 2. Electroless plating.
Electroplating:
Electroplating is defined as a process in which a base metal is coated with a thin layer of noble
metal by electrolytic deposition.
Ex: Coating of Cu on Fe, Au on Cu, Ag on Cu etc.
Electroless Plating:
Electroless plating is a technique of depositing a noble metal from its solution on a catalytically
active surface of the substrate by using Reducing agent and without passing electrical energy.
Metal ions + Reducing agent Metal + Oxidized product.
Significance or factors of electroplating process:
The important factors that control the process of electrolysis in electroplating are,
i) Polarisation ii) Decomposition Potential iii) Over voltage.

Polarization:
Polarization is an electrode phenomenon. The electrode potential is determined by
E= Eo + 0.0591/n log (Mn+)
Where Mn+ is concentration of metal ions surrounding the electrode surface at equilibrium. In an
electrochemical cell there will be anode and cathode when there is passage of current, oxidation
takes place at anode liberates electron, at cathode reduction take place. Metal ion accepts e- from
anode and converted to a metal, it is deposited at the electrode.
The metal ion concentration in the vicinity of the electrode surface decreases owing to the reduction
of metal ions; as a result there exists a concentration gradient between the bulk of the solution and
the area surrounding the electrode surface which leads to diffusion of ions from the bulk of the
solution towards the electrode surface. If the diffusion is slow, the electrode potential changes and
electrode is said to be polarized. At anode polarization is due to excess accumulation of ions on the
electrode.
Polarization is defined as a “process in which there is a variation in electrode potential due to slow
supply of ions from the bulk of the solution to the electrode”.
Electrode polarization depends on several factors
 Nature i.e size, shape, and composition of the electrode
 Electrolyte concentration and its conductivity
 Temperature
 Rate of strring of the electrolyte
 Products formed at the electrodes
Decomposition potential (discharge): It is defined as “The minimum external potential or

voltage is required for the continuous electrolysis of the electrolyte”.

Experimental determination of Decomposition potential
The cell consists (fig.1) of two Pt electrodes immersed in dil solution of acid or base. Voltage is
varied by moving the sliding contact (D).On the wire AB current passing through the cell is
measured using ammeter. At low voltage no reaction occurs and there is slight increase in current, on
increasing the voltage slightly above there is abrupt increase in current and sudden evolution of H2
and O2 takes place. The applied voltage is called decomposition potential of acids or base.
A typical voltage V/S current graph is plotted. (Fig.2) The intersection of the two straight line
portions of the graph gives the decomposition potential.
Over voltage
It is defined as the “Excess voltage is to be applied over and above the theoretical decomposition
potential of an electrolyte, to start the electrolysis of the electrolyte”.
Over voltage = ŋ = Experimental decomposition- theoretical decomposition

potential potential
Eg: In electrolysis of water the actual voltage at which electrolysis occurs is 1.7V.Therotical voltage
ought to have occurred 1.23V
Over voltage = 1.7-1.23=0.47V
Over voltage depends on 1) Nature and physical state of the metal electrodes.
2) Current density
3) Temperature
4) Nature of the substances deposited
SURFACE PREPARATION:
It is very much necessary to clean the surface of the base metal before electroplating in order to get a
good deposit. The impurities found on the surface may be grease, oxide film, oil, dust, etc. Various
methods available to clean the surface of the metal are:
 Solvent cleaning: Organic solvents (acetone, ether, etc) are used to remove impurities like
oil, grease, etc., from the metal surface.
 Alkali cleaning: This is employed to remove old paint from the metal surface by using
solutions of NaOH, sodium silicate, sodium carbonate etc.
 Pickling: This is used to remove oxide scale from the surface by dipping in dilute HCl or
H2SO4 .
 Mechanical cleaning or polishing : is used to remove loose rust and other impurities from
the surface. Strong adhering scales are removed by using silicon carbide grinding wheels,
emery paper, knife, etc..
 Rinsing and drying: After cleaning the metal surface, then the metal should be rinsed with
distilled water.

Electroplating Process of Chromium: (Decorative and Hard)
Sl.No Particulars Sulphate bath Sulphamate bath

(Decorative chromium) (Hard chromium)
Bath 250g chromic acid +2.5g H2SO4
1 250g of chromicacid+25gH2SO4/L
composition /Lt.+ 4.5g oxalic acid
Operating
2 313-318 K 313-328K
temperature
Current
3 20-40 mA/cm2 20-40 mA/cm2
density
4 pH 5.7 8.4
Insoluble anodes Pb-Sn alloy or Insoluble anode Pb-Sn alloy or

5 Anode
PbO2 PbO2
6 Cathode Object to be plated Object to be plated
Phenol sulphonic acid, Aromatic

Organic Phenol sulphonic acid, Aromatic
7 sulphonates, Alkyl sulphonates,
additives sulphonates, Alkyl sulphonates, etc.
etc.
2- +
CrO3 + H2O ----- H2CrO4 ------ CrO4 + 2H
2H2CrO4 ------ H2Cr2O7 + H2O ----Cr2O72- + 2H+ + H2O
Cr2O72- + 14H+ + 6e ------ 2Cr3+ + 7H2O
Cr3+ + 3e- ------ Cr
Chromium anodes are not used in Cr plating because chromium metal passivates strongly in acid
sulphate medium. Chromium on dissolution gives Cr 3+ ions, large concentration of Cr3+ ions forms a
black deposit of chromium on cathode.
Electroless Plating
Electroless plating is a technique of depositing a noble metal from its solution on a catalytically
active surface of the substrate by using Reducing agent and without passing electrical energy.
Metal ions + Reducing agent Metal + Oxidised product.

Electroless plating of Copper
Conducting salt : Copper sulphate (12g/litre)

Reducing agent : Formaldehyde (8g/litre), Sodium hydroxide
pH : 11
Temparature : 298 K
Buffer solution : Rochelle salt (14g/litre)
Complexing agent : EDTA
Chemical reaction: Cathode: Cu2+ + 2e- 2Cu

Anode : 2H-CHO+4OH- 2H-COO-+2H2O+H2+2e-
Overall reaction: Cu2++2H-CHO+4OH- 2HCOO- + 2H2O + H2 + 2Cu
Application: Used in the preparation of printed circuit boards.
Electroless plating of Nickle:-
Pretreatment and activation of the surface:- The surface to be plated is first degreased by using
organic solvents or alkali followed by acid treatment. In the case of non-metallic article, the
surface is treated with SnCl2 and PdCl2 and in the case of metals like Al, Cu, Fe etc, the surface
is directly nickel plated without activation.
Conducting salt :- Nickle chloride

Reducing agent :- Hypophosphate (5gm/dm3)
pH :- 4–5
Temperature :- 930C
Buffer :- Sodium acetate
Complexing agent :- Sodium succinate (3gm/dm3)
Chemical reaction : (Redn.reaction) Ni2+ + 2e-  Ni
(Oxida.reaction) H2PO2- + H2O  H2PO3- + 2H+ + 2e-
Overall Reaction: Ni2+ + H2PO2- + H2O  Ni + H2PO3- +2H+
Applications:- Electrolessplating of nickel finds application in pressure vessels, pumps,

hydraulic compressors, in domestic and automotive fields.

Difference between electroplating and electroless plating.
Sl.
No Property Electroplating Electroless plating
.
1 Driving force current Autocatalytic redox reaction
n+ -
2 Anodic reaction M M + ne R Ox + ne -
3 Cathodic reaction Mn++ne- M Mn++ne- M
4 Anode Separate anode Catalytic surface of substrate
5 Cathode Object to be plated Object to be plated
6 Reducing agents electrons Chemical reagents
7 Applicability Only to conductors Conductors and non conductors
Advantages of electroless plating

1. No electrical power is required,
2. Plating may also be obtained on insulators and semiconductors,
3. Better throwing power compared to electroplating,
4. Even irregular shapes can also be plated uniformly
5. The plating possess unique mechanical, chemical and magnetic features.
Assignment Questions
1.Define Electroplating and Electroless plating.

2.Describe technological importance of metal finishing.
3.Explain (i) Polarisation, (ii) Decomposition potential and (iii) Over voltage.
4.Explain the electroplating of Chromium.
5.Explain the electroless plating of Nickel.
6.Explain the Electroless plating of Cu.
Course Outcomes: Upon successful completion of this course, students will be able to
 Explain fundamental concepts of corrosion,corrosion control and surface modification
methods namely electroplating and electroless plating.

MODULE-3
ENERGY SYSTEMS (CO 3)
Chemical Fuels: Introduction, Classification, Calorific value – gross and net calorific values,
Determination of calorific value of fuel using Bomb calorimeter, numerical problems. Knocking of
petrol engine-Definition, mechanism, ill effects and prevention. Power alcohol, unleaded petrol and
biodiesel.
Fuel Cells:- Introduction, differences between conventional cell and fuel cell, limitations and
advantages. Construction, working and applications of methanol-oxygen fuel cell with H2SO4
electrolyte, and solid oxide fuel cell (SOFCs).
Solar Energy: Introduction, construction and working of typical PV cell.Preparation of solar grade
silicon by Union Carbide Process/Method. Advantages and disadvantages of PV cell.
FUELS:
Definition of Fuel:-
A fuel is a substance made up of hydro carbons which upon combustion releases energy in the form
of heat or light which can be used for any useful purposes. During combustion fuels release carbon
dioxide.
Classification of fuels:-
On the basis of origin, fuels are classified as primary and secondary fuels. These are further
classified as solids, liquid and gaseous fuels.
a) Primary/Natural fuels:- These are fuels which occur naturally and do not need any
processing and can be used directly. Ex: - wood, coal etc.,
b) Secondary/Derived fuels: - These are the fuels which are derived from primary fuels by
chemical processing of primary fuels. Ex: - petroleum products, coke etc.,
Physical state Primary Secondary

Solid Wood, coal Charcoal, coke
Liquid Crude Petroleum Kerosene, diesel
Gaseous Natural gas Coal gas, water gas, producer gas
Calorific value:-
It is defined as the amount of heat liberated when a unit weight of fuel is burnt completely in
presence of oxygen. It is expressed in cal/g or Kcal/g.In SI units it is expressed as J/Kg or KJ/Kg
Types of calorific value:-
There are two types;
a) Higher calorific value/Gross calorific value: - It is defined as “the amount of heat liberated
when a unit weight of fuel is burnt completely in presence of oxygen and the combustion
products are cooled to room temperature (288K)”.
Fuels contain hydrogen when calorific value of fuel containing H 2 is experimentally determined
the H2 will be converted into steam and when products of combustion is brought down to room

temperature the latent heat of condensation of steam gets included in heat measured. Therefore
calorific value will be higher than normal value. Hence it is called H.C.V.
b) Lower calorific value/Net calorific value (LCV):- It is defined as “the amount of heat liberated
when a unit weight of fuel is burnt completely in presence of oxygen and the combustion
products are allowed to escape into the atmosphere”.
Here water vapor and moisture are not condensed and they are allowed to escape other hot
gases. So lesser amount of heat energy is available. Therefore calorific value will be little
lesser than normal value. So it is called lower calorific value.
LCV = HCV-Latent heat of water vapor formed
Experimental determination of calorific value of solid or liquid fuels by Bomb calorimeter:-

The calorific value of solid and liquid fuels can be determined experimentally by using Bomb
calorimeter.
The calorific value is determined by burning a known mass of fuel in oxygen under high pressure.
Construction:-
It consists of strong cylindrical vessel(BOMB) with capacity of 400-500ml. It has air tight screw lid
with valve for pumping oxygen.The bomb is placed in copper calorimeter which is surrounded by air
and water jacket to prevent loss of heat due to radiation. The calorimeter is provided with electrical
stirrer and Beckmann’s thermometer, which can be read up to 100 th part of degree. A known mass
of fuel (about 1g) in form of pellet is taken in ceramic or platinum crucible. A loop of iron wires are
projected out are connected to electric source, it is placed in bomb the apparatus is placed in a
weighed amount of water taken in the vessel (calorimeter).
Oxygen
Stirrer
B
Wires for ignition

Thermometer
Lid
Sample
Working:-
The initial temperature of water is noted (t10C). A known mass of fuel (about 1g) whose C.V. is to
be determined placed in crucible is ignited through the electric current so rapid combustion of fuel
takes place. Then water in the calorimeter is continuously stirred using an electrical stirrer during
heating. The maximum temperature attained by water is noted (t 20C).

Observations and calculation:-

Mass of fuel is crucible = mg
Mass of water in calorimeter = Wg
Water equivalent of calorimeter = w g
Initial temperature of water = t 1ºC
Final temperature of water = t2ºC
Rise in temperature of water = (t 2º- t1º)ºC
Specific heat of water = S J/Kg/ºC
Heat liberated due to combustion of fuel = mQ
Heat absorbed by water and other apparatus = (W+w) (t 2º- t1º)
But heat absorbed = heat liberated Therefore (W+w) (t2º- t1º) xS
The calorific value is determined by using the equation
Q= (W+w) (t2º- t1 º)XS

m
LCV = HCV – (0.09 X %H X Latent heat of steam

LCV = HCV – (0.09 X %H X 587) cal/g
Problems:
1. When 0.935g of fuel undergoes complete combustion in excess of O2 the increase in
temperature of water in calorimeter containing 1365g of water was 2.4 0C.Calculate HCV
of fuel if water equivalent is 135g
Data:
Mass of fuel m = 0.935g =0.935X10-3Kg
Mass of water W = 1365g = 1365X10-3kg
Water equivalent w = 135g = 135X10-3kg
Rise in temperature = 2.40C
Solution:
Q= (W+w) (t2º- t1º)XS
m
= (1365 + 135)X10-3x 2.4 x 4.187
0.935X10-3
=16,121.06 KJ/Kg
2. When 0.5g of coal is burnt in a bomb calorimeter, the rise in temperature was found to be
4.80C. Calculate the calorific value of coal sample. (Given water equivalent of calorimeter
as 2.00kg and specific heat of water is 4.18KJ/Kg/ 0C) [VTU Mar 1999]
Solution:
Q= W (t2º- t1º) xS
m

= 2 x 4.187x 4.8
0.5X10-3
= 80256KJ/ Kg
3. 0.8gms of coal sample with 92% C, 5% H2 and 3% ash caused a rise in the temperature of
4000gm of water by 6.2 oC in a bomb calorimeter experiment. Calculate the Gross and Net
calorific value of coal, given: water equivalent = 400gm, Specific heat of water = 4.187 KJ
Kg-1oC-1, Latent heat of steam = 580calories/gm % of H2 =5 (1 calorie = 4.18 Joules).
Solution: Formula: GCV= (W+w) S (t 2-t1)

m
GCV= (4000+400) *10-3*4.187*6.2
0.8*10-3
GCV= 142776.7 KJ/Kg
NCV= GCV - 0.09  % H  latent heat of steam
NCV= 142776.7- [0.09*5*580*4.18]
NCV= 141685.72 KJ/Kg
4. The gross calorific value of a sample of bituminous coal is 36000 KJ/Kg. In an experiment, 0.83g of
this coal was burnt under 1.2 Kg of water in a bomb calorimeter. Due to combustion, the
temperature of water rose by 3.920C. Calculate the water equivalent of calorimeter, specific heat of
water = 4.2KJ/Kg/0C.
Gross calorific value = 36000KJ/ Kg
Mass of bituminous coal = 083 x 10-3 Kg
Mass of water = 1.2kg Rise in temperature=3.920C
Specific heat of water = 4.2KJ/Kg/0c.
GCV= (W+w) S (t2-t1)
m
36000 = (1.2+w) *4.2*3.92
0.83 x 10-3
w = 0.615Kg
5. Calculate the gross and net calorific value of a coal sample from the following data obtained from
bomb calorimeter experiment.
i. weight of coal (m) = 0.73g
ii. Weight of water taken in calorimeter (W) = 1500g
iii. Water equivalent of calorimeter (w) = 470g
iv. Initial temperature (t1) = 250C
v. Final temperature (t2) = 27.30C
vi. Percentage of hydrogen in coal sample = 25%
vii. Latent heat of steam = 587cal/g (1 cal = 4.18J)

viii. Specific heat of water = 4.187 KJ/Kg/0C
GCV = (W+w) S (t2-t1)
m
= (1500 +470)*10-3 *4.187*(27.3-25) =
0.73* 10-3 GCV = 25,988.1 KJ/Kg
NCV = GCV-heat released by the condensation of steam

= 25,988.1 – 0.09*25*587*4.187
= 20,467.3 KJ/Kg
6. On burning 1.15g of a coal sample in a bomb calorimeter, the temperature of 3.5kg of water in the
calorimeter increased from 26.50C to 28.50C. Water equivalent of calorimeter is 325g. Specific heat
of water is 4.187KJ/Kg/ 0C and latent heat of steam is 2458J/g. If the fuel contains 4% hydrogen,
calculate its gross and net calorific values. [June/July - 2011]
GCV= (W+w) S (t2-t1)
m
= (3.5 +325x10-3)x4.187x(28.5-26.5)
1.15x10-3
= 27,852.65 KJ/Kg
NCV = GCV-0.09x% H2xlatent heat of steam
= 27,852.65 -0.09 x 4 x 2458
= 26967.77 KJ/Kg
Assignment Questions
1. Define chemical fuel. How are the fuels classified?
2. Define calorific value. Explain the types of calorific value.
3. Explain the determination of calorific value of a solid fuel using bomb calorimeter?
6. Calculate the calorific value of a coal sample from the following data:
Mass of coal = 1g, weight of water in calorimeter = 2.0g,
Specific heat of water =4.187KJ/Kg0C and rise in temperature = 4.80C.
7. Calculate the gross calorific value and net calorific value of a coal sample from the
following data.
i. Weight of coal (m) = 8.5x10-4kg
ii. Weight of water taken in calorimeter (W) = 3.5kg
iii. Water equivalent of calorimeter (w) = 0.5kg
v. Final temperature (t2) = 27.50C
vi.Percentage of hydrogen in coal sample = 2.5
vii. Latent heat of steam = 2455kj/kg

8. Calculate the gross calorific value of a coal sample from the following data.
i. Weight of coal (m) = 5.5x10-3kg
ii. Weight of water taken in calorimeter (W) = 3.4kg
iii. Water equivalent of calorimeter (w) = 0.5kg
v. Final temperature (t2) = 280C
9. A 0.6g coal sample with 92% C, 5% H2 and 3% ash, caused a rise in the temperature of 2000g of
water by 3.20C in a bomb calorimeter experiment. Calculate the gross and net calorific value of
coal, given water equivalent = 200g, specific heat of water = 4.187KJ/Kg/0C, latent heat of steam
= 580 cal/g (1 calorie = 4.18 Joules)
10) 0.78g of coal containing 1.9% H2 , when burnt in a bomb calorimeter , increased the
temperature of 2.7 Kg water from 27.2˚C to 29.2˚C .If water equivalent of calorimeter is 1.2 Kg.
Calculate GCV and NCV (Specific heat= 4.187 KJ/Kg/˚C, latent heat of steam = 2457 KJ/Kg )
11) Calculate the calorific value of a coal sample of coal from following data.
Mass of coal = 0.95 g
Mass of water in calorimeter = 2000g
Water equivalent calorimeter = 700g
Rise in temperature = 2.8˚C
Specific heat of water = 4.187 KJ/Kg/˚C
PETROLEUM:
Definition: Petroleum is primary liquid fuel which is brown to black colour. Crude petroleum is
mixture of hydrocarbons. In addition it also contains organic compounds, Nitrogen, Oxygen and
Sulphur.
Gasoline Knocking:
Knocking is defined as “ the production of shock wave in an IC engine as a result of an
explosive combustion of fuel – air mixture due to increase in compression ratio , beyond a
certain value, leading to a rattling sound ”
In internal combustion engines a mixture of gasoline and air is used as a fuel. The combustion is
initiated by a spark in the cylinder. The flame thus produced spreads rapidly and smoothly through
the gaseous mixture. When petrol undergoes combustion under ideal conditions the pressure inside
the cylinder generally rises and the rate of flame propagation is about 20-25m/s. Beyond a particular
compression ratio, the petrol-air mixture suddenly burst into flames and the fflame propagation rises
to 2500m/s. This explosive combustion raises the gaseous pressure inside the cylinder and this
pressure dissipates its energy to the cylinder walls producing a characteristic rattling sound which is
called as knocking.

Disadvantages of knocking:
1) It produces undesirable rattling sound leading to noise pollution.
2) It increases the fuel consumption

3) It results in decreased power output.
4) It causes mechanical damage by overheating the engine parts.
Mechanism of Gasoline Knocking:
Under normal conditions, slow oxidation of fuel will occur, during this O 2 combines slowly with a
few hydrocarbon molecules and activates them. The activated molecules combine with hydrocarbon
molecules to establish a smooth and slow chain reaction resulting in smooth combustion of fuel.
C2H6 + 7/2 O2 2CO2 + 3H2O
But when chain reaction occurs at a very fast rate, the hydrocarbon molecules combine with O2 to
form unstable peroxides. This unstable peroxide decomposes to give a number of gaseous
compounds. This gives rise to pressure waves which knock against the engine walls producing
rattling sound.
C2H6 + O2 → CH3-O-O-CH3
Ethane peroxide
CH3-O-O-CH3 → CH3-CHO + H2O
Acetaldehyde
CH3-CHO +3/2 O2→ H-CHO + 2CO2 + H2O
Formaldehyde
H-CHO + O2 → CO2 + H2O
Antiknocking agents:
These are the substances that are added to the gasoline to prevent knocking. The common
commercial antiknocking agents used are
i) Tetra ethyl lead (TEL) ii) Tetra methyl lead (TML) iii) Mixture of TEL + TML
Among this TEL is most widely used since it is cheap and more effective in increasing the octane
rating of fuels. It is normally used along with ethylene dibromide or ethylene dichloride.
It is believed that during combustion of gasoline TEL forms Pb and PbO. These species inhibits the
propagation of explosive chain reaction and thereby minimizing the knocking.
Unleaded Petrol:-
In order to enhance the octane rating of petrol,it is normally mixed with TEL. But this mixing with
TEL leads to liberation of Pb vapours to air.Pb is major air pollutant. Hence in place of TEL,petrol is
mixed either with methyl-t-butyl ether or ethyl-t-butyl ether or methanol which have same octane
number as that of TEL.Such petrol which is free from lead content is known as unleaded petrol.
Power alcohol:
Power alcohol is a blend of absolute alcohol with petrol. In this the absolute alcohol is blended with
petrol to avoid phase separation. Power alcohol is prepared by blending 25% of absolute alcohol
with petrol.

Importance of power alcohol:

1. Power output is good.
2. Addition of ethanol to gasoline promotes efficient combustion of gasoline which reduces the
emission of carbon monoxide and volatile gases. There by reducing the air pollution.
3. It has better antiknocking property. Hence it can be used in engines with high compression
ratio.
4. Petrol-alcohol blend has same lubrication as petrol.
5. It is a biodegradable fuel.
6. Air required for complete combustion is less.
Bio Diesel :
Bio diesel is non-toxic, biodegradable replacement for petroleum diesel. Bio diesel is a source of
energy which is renewable, oxygenated fuel made from variety of vegetable oils such as soyabean,
corn etc.
Production of Bio diesel:
It is produced by trans-esterification of vegetable oil or animal fat in presence of alcohol and a
catalyst(NaOH). The resulting mixture of monoalkyl esters of fatty acids obtained is referred to as
bio diesel.
CH2OCOR1
CHOCOR2 3CH3OH NaOH (catalyst) CH2OH

+ 3CH3COORx +
CH2OCOR3 CHOH
Bio diesel
Vegetable oil CH2OH
Glycerol
Advantages:
 It is less noxious and non-toxic
 It is biodegradable
 Can be produced from waste vegetable oil
 Prolongs engine life
 Bio diesel has higher cetane number
 Burns more efficiently than petroleum, diesel
 It acts as carbon neutral i.e, bio diesel use does not lead to any overall change in the amount
of CO2 in the atmosphere
 It is a renewable since it is derived from vegetable oil which is essentially grown a
sustainable resource.

Assingment Questions
1. Define knocking in IC engine? Explain the mechanism of knocking.

2. Explain Bio-diesel.
3. Explain the term power alcohol. Mention the importance of power alcohol as fuel.
4. Write a note on unleaded petrol.
FUEL CELLS:-
Fuel cells are the galvanic cells in which chemical energy of fuel is directly converted into electrical
energy .In fuel cells the reactants (fuel) are continuously supplied to the cell and at the same time the
products are removed from the cell as soon as it is formed in the cell. The energy will be liberated as
long as the reactants are supplied.
Differences between battery and fuel cell:

Battery Fuel cell
1. In battery chemical energy is stored 1. Chemical energy is not stored
2. It needs recharging 2. It does not require recharging
3. Efficiency gradually decreases 3. Efficiency remains same and it is highly
efficient compared to battery
4. Non ecofreindly 4. Eco friendly
Advantages of fuel cells:-

1) Efficiency is very high when compared to conventional cells.
2) By products formed are harmless because they do not make any environmental
Pollution
3) There is no self discharge.
Limitations of fuel cell :-
1) The electrodes used are either Pt, Ag or the alloys of noble metal which are costly.
2) Fuels in the form of gases and oxygen need to be stored in tanks under high pressure.
3) Power output is moderate.
Methanol-Oxygen fuel cell:-
In Methanol-oxygen fuel cell both anode and cathode is made up of platinum. A membrane is
inserted adjacent to the cathode on inner side to minimize diffusion of methanol into the cathode
thereby reducing the concentration of methanol near the cathode. In the absence of the membrane,
methanol diffuses through the electrolyte into the cathode and undergoes oxidation. Sulphuric acid is
the electrolyte in this cell. Methanol containing some sulphuric acid is passed at anode electrode.
Pure oxygen is passed through the cathode electrode.
An advantage of using H2SO4 as electrolyte is that CO2 is formed as one of the product
which can be removed easily. This cell produces a potential of 1.20V.

Anode : CH3OH + H2O → CO2 + 6H+ + 6e-

Cathode: 3/2O2 + 6H+ + 6e- → 3H2O
CH3OH + 3/2O2 → CO2 + 2H2O
The methanol-oxygen fuel cell is used in military applications and in large scale power production.
Solid Oxide Fuel Cell:- (SOFC)

The solid oxide fuel cell operate at the high temperature at around 10000C.The electrolytes used are
solid oxide material
Instruction:- An SOFC consists of two porous electrodes separated by a dense, oxygen ion
conducting electrolyte.The anode is a porous cermet(composite material composed of ceramic and
metal) made of metallic nickel(Ni) and Yettria-stabilized zirconia . The cathode strontium-doped
lanthanum manganate.Electrolyte is Yettria-doped zirconia (YSZ) is used as oxygen-conducting.
Solid oxide fuel cells are a class of fuel cells characterized by the use of a solid oxide material as the
electrolyte. SOFCs use a solid oxide electrolyte to conduct negative oxygen ions from the cathode to
the anode. The electrochemical oxidation of the oxygen ions with hydrogen or carbon monoxide thus
occurs on the anode side.
ANODE :- H2 + O2- --------- H2O + 2e-

CO + O2- ------- CO2 + 2e-
CATHODE:- O2 + 4e- ----- 2O2-
Applications:- SOFCs have wide range applications ,such as working as power systems for trains,

ships , supplying electrical power for residential or industrial utility.
SOLAR ENERGY
Introduction:
Solar energy is one obtained from Sun, which has unlimited amount of energy, which is generated
due to nuclear fusion reaction of hydrogen into other elements taking place in the Sun. It radiates
energy in the form of heat and light.
Increasing consumption of energy to meet the demands of civilization has led to many
environmental issues, hence it is time to find out and develop alternative energy sources, which
should be without delay, it is one viable alternative. Solar energy is renewable and its usage is very
bright indeed. The most convenient application of solar energy is in heating of buildings and
providing hot water.
Solar energy can be utilized in two different ways. Direct solar power and indirect solar
power. Direct solar power-This involves converting to directly into electricity by making use of
photovoltaic devices. Indirect solar power involves more than one transformation to reach a usable
form, for eg., Plants absorb energy from Sun through the process of photosynthesis to convert solar
energy to chemical energy which can later be burnt as fuel to generates electricity. The devices
commonly used for harnessing solar energy are solar cookers, solar water heaters in which energy is
collected in form of heating other type solar energy is converted into electricity like in a solar cells.
Photovoltaic cells:
Photovoltaic cells or solar cells as they are often referred to are semiconductor devices that convert
sunlight into direct current electricity.
Photovoltaic cell id based on photoelectric effect. The photoelectric effect was first noted by
Edmund Becquerel.
Construction of photovoltaic cell :
A typical silicon photovoltaic cell consists of a metallic layer made up of aluminum on top of it
silicon wafers are placed consisting of an ultra thin layer of phosphorus doped (n- type) silicon on
top and boron doped (p-type) silicon at the bottom of the wafer which forms p-n junction. Front and
rare sides of the wafer are finger printed with silver paste. Above the silicon wafers an antireflective
layer which is made up of very thin layers of silicon nitride or titanium dioxide, this to increase the
amount of light transmitted by semiconductor. Metallic grids are placed between the antireflective
layer to form electrical contact and to allow the light to fall on semiconductor.
Antireflective
layer
sunlight
Metal grid
n-type
layer
p-type
h+ layer
e- n-type
layer
h+
e-
Global Academy of Technology, RR nagar , Bengaluru Metallic layer 42

Working of photovoltaic cell

Semiconductors have the capacity to absorb light and to deliver a portion of energy of absorbed
photons to carriers of electrical current electrons and holes.
A typical silicon photovoltaic cell composed of thin wafer doped Phosphorous (n-type) and boron
doped(p-type) silicon hence p-n junction is formed. When light radiation falls on the p-n junction
diode, electron-hole pair are generated by the absorption of the radiation. The electron are drifted to
and collected at the n-type and holes are drifted to and collected at the p-type end. When these two
ends are electrically connected through a conductor, there is a flow of current between the two ends
through the external circuit. Thus photoelectric current is produce and available for use.
The main advantages of PV cell are:
 They need no charging
 They are environment friendly
 They do not corrode
 They operate at ambient temperature
 They are abrasive resistant
Disadvantages of PV cell
 Power efficiency of a commercial Si based PV cell is very low

 Power production mainly depends on availability of sun light.
 Silicon required for PV cell is of high purity.
 Economical costly compared to other conventional cells.
Solar Grade Silicon:

The common material used for solar cells is crystalline silicon or multi crystalline wafers or ribbon
silicon drawn from molten silicon.
The silicon having these impurities in substantial amount, but within tolerable limit is called solar
grade silicon.
The purity of solar grade silicon lies between metallurgical grade silicon and semi conductor grade
silicon.
Production of solar grade (Crystalline) silicon: Union Carbide Method
The method involved in the production is:
The silica (quartz) is reduced with carbon (coal) by heating to 1500-2000◦C in an electrode arc
SiO2 + 2C Si + 22CO
+
This liquid silicon is collected at bottom of furnace and this is then drained and cooled. This silicon
produced is metallurgical grade silicon, which is 98% pure silicon.
The metallurgical grade silicon is further refined by reacting with anhydrous HCl at 300◦C in
fluidized bed reactor to form trichlorosilane this is called Siemens Process.

Si + 3HCl SiHCl3 + H2
22222
During this reaction impurities such as Fe, Al and B react to form their halides (Eg FeCl3,AlCl3 and

BCl3).SiHCl3 is purified by impurity halides by distillation.
2SiHCl3 ------ H2SiCl2 + SiCl4
3 H2SiCl2 ---- SiH4 + 2HSiCl3
silane
Silane undergoes pyrolysis at higher temperature to give semiconductor grade silicon.
HSiCl3 + H2 Si + 3HCl
The silicon produced is called polycrystalline silicon which has impurity level of 1 part per billion or
less.
The silicon thus obtained is further purified by Zone refining.
Describe the concepts of non-renewable(petroleum) and renewable(solar) energy sources,
Calorific value of fuel and fuel cell.
1. Discuss the importance of the photovoltaic cell.
2. Discuss advantages and disadvantages of photovoltaic cell?
3. Explain the construction and working of photovoltaic cell ?
4. Explain the method for production of solar grade silicon by Union Carbide method.
5. Illustrate the difference between battery and fuel cell.
6. Explain the construction and working of methanol oxygen fuel cell. Mention its applications.
7. Explain the construction, working and application of solid oxide fuel cell.

MODULE 4
ENVIRONMENTAL POLLUTION AND WATER CHEMISTRY
(CO 4)
WATER CHEMISTRY :
Introduction,sourcesand impurities of water,boiler feed water, boiler troubles with disadvantages &
prevention methods– scale and sludge formation,boiler corrosion (due to dissolved O2, CO2 and
MgCl2).Sources of water pollution, sewage,definition of COD and BOD,determination and
numerical problems on COD. Sewage treatment: Primary, secondary (activated sludge process) and
tertiary method. Softening of water by ion exchange process. Desalination of sea water by reverse
osmosis .Chemical analysis of water:Sulphates(gravimetry) and Fluorides(colorimetry).
ENVIRONMENTAL POLLUTION: Air pollutants: Sources, effects and control of primary air
pollutants: Carbon monoxide, Oxides of nitrogen an sulphur, hydrocarbons, particulate matter,
carbon monoxide, mercury and lead. Secondary air pollutants: Ozone, ozone depletion.
WASTE MANAGEMENT:
Solid waste, e-waste &biomedical waste: Sources, characteristic & disposal methods(Scientific land
filling ,composting, recycling and reuse).
WATER CHEMISTRY
Introduction: Water is the most abundant and useful compound on the earth. It covers nearly 72%
of the earth’s surface. Water gets evaporated continuously from ocean, rivers, and lakes which goes
into the atmosphere as clouds and comes down to the earth’s surface in the form of rain. During the
course of it’s downward journey...
Almost all water on earth, 97.2% is locked in the oceans, 2.1% from ice & glaciers.
The fresh water available in lakes, rivers & underground amounts only to 0.6%. And the remaining
0.1% is in the brine wells & salty water.
 Water is the most widely used chemical compound on earth.
 It is one among the three essentials of life i.e. air, water & food
 Water occupies 2nd position in the order of priority.
 It is not only essential for human beings, but also for plants & animals.
 Human body contains about 65.0% by weight of water in the form of blood and other body
fluids.
 The average intake of water per day by an individual is about 2.5 liters.
.
Sources of water
1. Surface water: It includes flowing water such as streams and rivers and still water like
ponds , lakes and reservoirs.
a) Rain water: It is the purest water of natural water as it is resulted by the evoparation of
surface water. Rain water dissolves atmospheric gases such as CO2, NO2, SO2 etc as well as
organic and inorganic suspended particles.
b) Sea water: Sea water contains 3.6% of dissolved salts of which 2.6% is NaCl. Other salts

present are sulphates, bicarbonates, bromides of sodium, potassium, magnesium etc.
c) River water : springs and rain water are the sources of river water. River water flowing
through the land collects lot of organic matter from decaying plants and near by habitats.
d) Lake water: It contains less dissolved impurities compared to river water but it contains lots
of organic matter.
2. Underground water: A part of rain water which falls on earth surface percolates into the
earth and continue its continues till it meets a hard rock where it may be stored or come in
the form of spring. Ground water contains less of suspended matter and high dissolved
mineral content.
IMPURITIES IN WATER
1. Dissolved gasses:
Presence of CO2, NH3, Sulphur such as Hydrogen sulphide etc.in water Impart foul smell
2. Suspended Matter / Impurities:
These are the insoluble matter in suspension which imparts turbidity, colour and odour to water.
a) Inorganic Impurities: Clay, Silica, Sand, Fe2O3, MnO2 etc.
b) Organic impurities : Decayed Plants leaf, Dead animals bacterias, algae, protozoa,
3. Microscopic matter:
The presence of microorganisms and pathogenic bacteria in water causes “Water borne
diseases”.
4. Dissolved salts: Carbonates, Bicarbonates, Chlorides, Nitrates, Sulphates of Sodium, Calcium,
Magnesium, Potassium, etc. present in water cause “hardness”.
5. Colloidal impurities:
Organic wastes like emulsified oil, dyes, ether, finely divided clay, proteins, amino acids, Clay,
Fe (OH)2 etc. produce turbidity.
Boiler Feed water:

Water used in boilers is referred to as boiler feed water. Water is mainly used in boilers for the
generation of steam for industries and power houses. The steam generated in boilers is being used
for various purposes like power generation, space heating, process heating, drying, sterilization, etc.
Natural water contains different kinds of dissolved and suspended matter and dissolved gases
as impurities. These impurities create variety of boiler problems. The extent of boiler problems
depends upon three parameters are purity of feed water, boiler design and pressure under which
boiler is operating.
A boiler feed water should correspond with the following composition:
1. Its hardness should be 0.2 ppm,
2. Its caustic alkalinity (due to OH-) should lie between 0.15 and 0.45 ppm.
3. Its Soda alkalinity (due to Na2CO3) should be 0.456 to1 ppm.
If boiler feed water contains excess impurities it results in many problems such as
a) scale and sludge formation, b) boiler corrosion.

Boiler troubles:
a) Scales and Sludges:
In a boiler, water is continuously converted into steam, the suspended matter and the
dissolved salts present in it may get deposited on the inner surface of the boilers. If these precipitates
form hard, dense and sticky (adherent) coating on the boiler surface, it is called scale. If the
precipitates formed within the boiler are soft, loose and slimy, are called sludes. Both scale and
sludge cause a number of problems in boiler units.
Scales Sludges
1. Scales are hard deposits which stick very
1. Sludges are soft , non adherent deposit
firmly to the inner surface of the boiler
2. Scales are very difficult to remove
2. Sludges can be removed easily
3. Sludges can transforms heat some extent

3. Scales are bad conductors of heat and are
and are less dangerous
more dangerous.
4. scales are formed by substance like CaSO4 4. Sludges are formed by substance like
and Mg(OH)2 MgCl2 and CaCl2
Mechanism of scale formation:

The deposition of suspended matter and dissolved salts leading to boiler scales and sludges
due to the following factors.
1. Precipitation of substance by chemical reaction.
Example: Calcium bicarbonate decomposes at high temperatures produces calcium carbonate
which has low solubility in water and hence forms scales.
Ca (HCO3) → CaCO3 + CO2 + H2O
2. Solubility of the calcium sulphate decreases along with increase in boiler temperature. Thus it also
gets precipitated out in the form of scales.
3. Silica reacts with calcium and magnesium present in water to form silicates of calcium and
magnesium. These silicates form hard and glassy scale on the inner surface of boiler.
Disadvantages of Boiler Scales formation:

1. Loss of Fuel: Scales are poor conductor of heat, so rate of heat transfer from boiler to water is
greatly reduced. So the consumption of fuel is much more than usual.
2. Lowering boiler efficiency: Due to scale formation, heat available to water is reduced and hence
more heat is required to produce steam. This causes overheating of boiler plates and tubes and thus
their life is reduced.

3. Boiler explosion: Since the scale acts as a heat insulator, the boiler metal is overheated. Due to
overheating, the metal expands until the scale on it cracks. When thick scales crack, the water
suddenly comes in contact with overheated boiler metal. This causes the formation of a large amount
of steam suddenly. This results in the development of high pressure inside the boiler which may lead
to a dangerous explosion.
4. Expenses of cleaning: Scales must be removed regularly and this cleaning process is very much
expensive.
b) Boiler Corrosion:
Corrosion is a phenomenon in which a metal surface wears out as a result of chemical and
electrochemical processes occurring under the influence of environment. The process of degradation
of the boiler surface by the attack of boiler feed water is called as boiler corrosion.
Corrosion in boilers due to the presence of i) dissolved oxygen ii) dissolved CO2 and
iii) Magnesium chloride
i) Presence of dissolved oxygen: Presence of dissolved oxygen is a major cause of boiler corrosion.
At the boiler temperature of about 350- 450˚C the dissolved oxygen reacts with iron and produces
rust as follows:
2 Fe + O2 + 2 H2O → 2 Fe (OH)2
2 Fe(OH)2 + O2 → Fe2O3 2H2O (Rust)
This process is repeats till all the dissolved oxygen is exhausted.
ii) Presence of dissolved CO2 : Presence of dissolved CO2 and mineral acids in the boiler feed water
causes boiler corrosion.
Carbon dioxide forms carbonic acid in presence of water.
H2O + CO2 → H2CO3 → H+ + HCO3-
The H+ ion causes corrosion of the metal surface. The HCO3- ions bind with iron gives Fe(HCO3)2,
which decomposes giving Fe(OH)2 and CO2 thus continuing the process.
Fe (HCO3)2 → Fe (OH)2 + CO2
iii) Presence of Magnesium chloride:

Presence of salts like MgCl2 and FeCl2 in the boiler feed water produces mineral acids during
hydrolysis. The acid produced causes corrosion of the metal surface.
MgCl2 + 2 H2O → Mg (OH)2 + 2 HCl
FeCl2 + 2 H2O → Fe (OH)2 + 2 HCl
Prevention of Boiler corrosion:

1. By removing oxygen: Deoxygenation can be done by the addition of chemicals to boiling water.
Oxygen can be removed by adding hydrazine and Sodium Sulphite.

N2H4 + O2 → N2 + 2 H2O
Na2SO3 + ½ O2 → Na2SO4
2. By removing Carbon dioxide: The amount of dissolved CO2 may be reduced by treatment
with ammonia.
2 NH4OH + 2 CO2 → (NH4)2 CO3 + H2O
3. Acid corrosion may be reduced by making the boiler feed water slightly alkaline.
Biological oxygen demand:
Definition:- B.O.D. of a sewage is defined as the amount of oxygen required by microorganisms to

oxidize the organic wastes present in one litre of waste water over a period of 5 days at 20 oC .
Characteristics of B.O.D parameter:

 The unit of B.O.D. is mg dm-3 or p.p.m.
 It is empirical and semi-permeable.
 It represents only biodegradable organic load in sewage. Strictly aerobic conditions are
needed.
 Determination is slow and time consuming method.
 It is an expression of how much oxygen is needed for microbes to oxidize the organic matter
in the sewage.
 It gives information about the following.
 Polluting power of sewage or its nuisance value
 The load of organic matter on the sewage treatment plants.
incubation period and another one is subjected for immediate DO determination and is called blank
titration.
Chemical Oxygen Demand (C.O.D):

A faster method of determing the amount of of oxygen required to oxidize both the biologically
oxidizable and biologically non-oxidizable organic and inorganic wastes is by evaluating the
chemical oxygen demand.
Definition:- C.O.D is defined as the amount of oxygen used while oxidizing the total organic load of
the sample with a strong chemical oxidant, potassium dichromate in acid medium. It is represented
in mg dm-3 or p.p.m.
Characteristics of C.O.D. parameter:
 It is satisfactory, qualitative method for measuring total organic load.
 It is preferable to B.O.D. as the results are reliable.

 Rapidly measurable parameter and needs about three hours for completion.
 In general, C.O.D >B.O.D., since both biodegradable and non-biodegradable organic load are
completely oxidized.
 When used along with B.O.D test, it gives biologically resistant organic matter.
Experimental determination of COD:

Principle: A known volume of the waste water sample is refluxed with K2Cr2O7 solution in sulphuric
acid medium. K2Cr2O7 oxidizes oxidizable impurities. The amount of unreacted K2Cr2O7 is
determined by titration with standard solution of ferrous ammonium sulphate. The amount of
K2Cr2O7 consumed corresponds to the COD of waste water sample. To find out this , a blank
titration without waste water sample is carried out.
Procedure: Pipette 25ml of waste water sample in a flask, add 10 ml of K2Cr2O7 solution followed
by 10 ml of 1:1 H2SO4. Add 1g of Ag2SO4 and 1g of HgSO4. Attach a reflux condenser and gently
reflux the contents for two hours. Cool and titrate against ferrous ammonium sulphate solution using
ferroin as indicator till the bluish green colour turns to reddish brown. Let the volume of titrant
required be y ml. Perform a blank titration in the same way without using waste water. Let the
volume of titrant required be z ml.
Calculation:
Volume of K2Cr2O7 required for the sample =( z – y) ml
COD of the sample = 8 × N FAS × (z –y) × 1000

25
Numerical Problems on COD
1. 25 cm3 of an industrial effluent when subjected to COD test required 22.5 cm3 of 0.50N
K2Cr2O7 for complete oxidation. Calculate the COD of the effluent of the sample.
Solution: N1 (water sample) = ?
V1 (water sample) = 25 cm3
N2 (K2Cr2O7) = 0.5 N
V2 (K2Cr2O7) = 22.5 cm3
WKT, N1V1 (water sample) = N2V2 (K2Cr2O7)
N2V2
ie. N1 =
V1

WKT, Mass/lt = Normality * Eq.Mass of Oxygen

N2V2
COD of waste water/ lt. = × 8 × 1000
V1
0.5 × 22.5 × 8 × 1000

= = 3600 mg of oxygen
25
2. 25 cm3 of waste water sample was mixed with 25 ml of K2Cr2O7 , acidified & refluxed.
The unreacted K2Cr2O7 acidified required 8.2 ml of FAS. In a blank titration 25 ml of K2Cr2O7
acidified required 16.4 ml of same 0.2 N FAS. Calculate the COD of the waste water sample.

N2 (FAS) = 0.2 N
V2 (FAS) = ( Vb-Va) Where, Vb = 16.4 ml blank titre value ogf FAS
Va = 8.2 ml actual vol. of FAS
WKT, N1V1 (water sample) = N2V2 (FAS)
N2 * ( Vb –Va)
ie. N1 =
V1

N2 *(Vb-Va) 0.2 ( 16.4-8.2) * 8 * 1000
COD of waste water/ lt. = * 8 *1000 = = 524.8 mg / lt.
V1 25
3. 25 cm3 of an industrial effluent when subjected to COD test required 8.3 cm3 of 0.001 M
K2Cr2O7 for complete oxidation. Calculate the COD of the effluent of the sample.
(The equivalent mass of K2Cr2O7 = 49 )
Solution:
1 Molarity (K2Cr2O7) = 6 Normality ( K2Cr2O7)
0.001 Molarity (K2Cr2O7) = 6 * 0.001 Normality (K2Cr2O7)
N1 (water sample) = ?
N2 (K2Cr2O7) = 6 * 0.001 N

V2 (K2Cr2O7) = 8.3 cm3
N2V2
ie. N1 = V1
WKT, Mass/lt = Normality × Eq.Mass of Oxygen
N2V2
COD of waste water/ lt. = × 8 × 1000
V1
6 × 0.001 × 8.3 × 8 × 1000

= = 15.936 mg of Oxygen / lt.
25
4. In COD experiment, 25 cm3 of an effluent sample required 9.8 cm3 of 0.001 M of K2Cr2O7
for oxidation. Calculate the COD of the sample.
Solution:
1 Molarity (K2Cr2O7) = 6 Normality ( K2Cr2O7)
0.001 Molarity (K2Cr2O7) = 6 * 0.001 Normality (K2Cr2O7)
N1 (water sample) = ?
N2 (K2Cr2O7) = 6 × 0.001 N
V2 (K2Cr2O7) = 9.8 cm3

N2V2
ie. N1 =
V1
N2V 6 × 0.001 × 9.8 × 8 × 1000

COD of waste water/ lt. = * 8 * 1000 i.e.,
V1 25
= 18.816 mg of Oxygen / lt.
5) 20 ml of sample of COD analysis was reacted with 10 ml of

0.25 N K2Cr2O7 and the unreacted dichromate required 6.5 ml of 0.10 N Ferrous ammonium
sulphate. 10 ml of same K2Cr2O7 and 20 ml of distilled water under the same conditions as

the sample required 26.0
ml of 0.10 N FAS. What is the COD of the sample?

N2 (FAS) = 0.1 N
V2 (FAS) = ( Vb-Va) Where, Vb = 26.0 ml blank titre value of FAS
Va = 6.5 ml actual vol. of FAS
WKT, N1V1 (water sample) = N2V2 (FAS)
N2 * ( Vb –Va)
ie. N1 =
V1
N2 *(Vb-Va) 0.1 ( 26.0-6.5) * 8 * 1000

COD of waste water/ lt. = * 8 *1000 = = 780 mg / lt.
V1 20
Sewage Treatment:
The treatment of domestic sewage is carried out three stages.
a) Primary (physical and chemical) treatment
b) Secondary treatment involving biological methods.
c) Tertiary treatment
a) Primary treatment:
The removal of coarse solids in the sewage water is effected by means of racks, screens, grid
chambers and skimming tanks. Then the water is passed into a sedimentation tank where it is
allowed to settle. The non settleable solids are removed by coagulation by treatment with
coagulating agents like alum, ferric chloride or lime.
b) Secondary treatment (Biological process): Activated sludge process

This process involves an aerobic biochemical oxidation or aeration. The sewage water after
sedimentation is subjected to aerobic oxidation, during which the organic matter is converted into
carbon dioxide, the nitrogen into ammonia and finally into nitrites and nitrates.
The waste water after the biological treatment is allowed to flow into large tanks where
biological treatment is carried out. Air is passed vigorously from the bottom of the tank in order to to

bring good contact between the organic wastes and bacteria in presence of air and sunlight. Under
these conditions, aerobic oxidation of organic matter occurs. The sludge is formed is removed by
settling or by filtration using membranes. A part of the sludge is reused and the rest is used as
fertilizer. The added sludge from the previous oxidation batch is known as activated sludge. It
contains aerobic bacteria and micro organisms.
The residual water is chlorinated to remove bacteria. The activated sludge operates at 90 - 95
% efficiency of BOD treatment. Then the water is sent to tertiary treatment for next stage
purification.
Tertiary treatment:
The process includes
i) Treatment with lime for the removal of phosphates as insoluble calcium phosphate.
ii) Treatment with S2- ions for the removal of heavy metal ions as insoluble sulphides.
iii) Treatment with activated charcoal to adsorb remaining organic compounds
iv) Treatment with alum to remove the colloidal impurities and reduces the BOD level.
Softening of water by Ion Exchange method:

Water softening is the process of reducing the dissolved salts of calcium, magnesium, iron in
water. In this method, softening of water is done by exchanging the ions causing hardness of water
with desired ions from ion exchange resin. An ion exchange resin is a cross-linked organic polymer
having high molecular weight. The functional groups which are attached to the chain are responsible
for ion exchange properties. Ion exchangers are two types
a) Cation exchangers b) anion exchangers
a) Cation exchangers: Cation exchangers containing functional groups such as carboxyl
(-COOH), phosphoric acid (- H2PO3) and Arsenic acid (-AsO3H2). These resins exchange cation
portion of the mineral by their hydrogen.
b) Anion exchangers: An anion exchange resin having –NH2, –NHCH3, -OH groups. They exchange
anion portion of the mineral by OH- ion.

Process: Water is passed through a cation exchange resin which removes the cations (Ca 2+, Mg2+,
Na+) present in it.
RH+ + Ca2+ → R Ca2+ + H+
RH+ + Na+ → R Na+ + H+
Where R is the rest part of cation exchanger
The water is then treated by passing it through an anion exchanger to remove the anions ( SO 42-, Cl- ,
NO3-, F-).
ROH- + Cl- → RCl- + OH-
2 ROH- + SO42- → R2SO42- +2 OH-
Where R is the rest part of anion exchanger
Regeneration of spent Resin:
The spent cation exchange resin is regenerated by treating with hydrochloric acid.
R Ca2+ + H+ → RH+ + Ca2+
An anion exchange resin is regenerated by sodium hydroxide.
RCl- + OH- → ROH- + Cl-
Advantages of ion exchange process:

 The process is completed in a few seconds.
 The process can be used to soften highly acidic or alkaline waters.
 Very low hardness (0-2 ppm) water is obtained.
 The use of chemicals is minimized.
 The exchanger can be regenerated and used over and over again.

DESALINATION:
The process of removal of dissolved salts from the sea water becomes usable is described as
desalination.
The important methods of desalination are:-
(a) Reverse Osmosis
Reverse Osmosis
Osmosis is the physical movement of a solvent (water) through a semi-permeable membrane.
If pure water and salt water are separated by a semi permeable membrane, the water molecules flow
from pure water (dilute solution) to salt solution (concentrated solution). This process of movement
of solvent (water) molecules from dilute solution into concentrated solution through semi permeable
membrane is called osmosis. The pressure exerted by this transfer is known as osmotic pressure.
Water can be made to flow in reverse direction (from salt water to pure water) by applying pressure
on salt water which is greater than osmotic pressure.
Reverse osmosis is a method of producing pure water by forcing saline or impure water
through a semi permeable membrane across which only water molecules pass but not salts or
impurities.
Process: A reverse osmosis unit is simple and consists of a membrane, a vessel and a high pressure
pump. The membranes are generally made up of cellulose acetate or nylon . Reverse osmosis can be
effected by the use of pressure in the range of 410 – 540 psi. In this cell, sea water to be desalinated
is separated from fresh water through semi permeable membrane. A high pressure is applied to the
saline water. As a result of reverse osmosis, fresh water fresh water moves down and can be
collected from outlet at the bottom of the cell.
Determination of Fluoride in the given water sample.

Fluoride content in the water is determined by colorimetric or spectrometric method:-
Principle:- This method utilizes the reaction between fluoride and a complex of zirconium ion with
an organic reagent SPANDS [Sodium 2-(parasulphophenylazo)-1,8-dihyfroxy-3,6-naphthalene

disulphonate]. The fluoride reacts with the complex, dissociating a portion of it in a colorless ion,
(ZrF2-) and the reagent.

1. As the amount of fluoride increases, the color produced by Zr-SPANDS complex becomes
progressively lighter.
2. A calibration curve is obtained by treating a standard solution of fluoride with the complex,
anf measuring the absorbance and plot the graph of absorbance V/s concentration of fluoride.
3. By measuring the absorbance, the amount of fluoride present in the sample of water can be
determined.
4. The method is subject to errors due to interfering ions and it is necessary to separate the
fluoride from the sample by distillation.
Procedure:-
a) Preparation of the reagent:-
1) 950mg of SPANDS + 500ml of distilled water.
2) 133mg of Zirconyl chloride octahydrate (ZrCl2.8H20) + 25ml of distilled water.
3) Add 350ml of conc.HCl+ 500ml of distilled water.
4) Mix equal volumes of SPANDS solution and Zirconyl acid reagent.
b) Preparation of calibration curve:-
1) 0.221g of sodium fluoride + 1lt of DM water + stock solution is diluted such that it has 10mg
per liter of fluoride.
2) Pipette out 1,2,3,…..8ml of the solution in 50ml of std flask + add 10ml of the Zirconyl-
SPANDS reagent to each of the solution ,make up to solution and mix well..
3) Measure the absorbance of the solution at 570nmagainst blank solution.
4) Plot the graph of absorbance v/s concentration.
Determination of Fluoride content in the water:-

1) Distillation flask:- 400ml of DM water +200ml of sulphuric acid, mix well + add glass beads
and distillation flask is maintained at 1800C.
2) At this temperature stop heating and discard the distillate.
3) Cool the acid mixture in the distillation flask to 1200C or below + add 300ml water sample,
mix thoroughly and distill as before until the temp reaches to 1800C.
4) Pipette out a known volume of distillate obtained into a 50ml std flask , add 10ml of
Zirconyl-SPANDS reagent, make up to the mark, shake well and measure the absorbance as
before.
5) From the calibration curve, conc of fluoride in the test solution can be determined.
Determination of Sulphate in the given water sample :-(Gravimetrically)
Sulphates occur naturally as a result of leaching from sulphur deposits in earth.

Principle:- Determination of sulphate in water is done by gravimetric procedure using barium. If

Ba2+ solutions are added to the sample in acidic media, where sulphates are precipitated as BaSO4.
The reaction mixture is heated for 2 hours at 80-90oC. The BaSO4 precipitate is then washed,dried at
130oC,and weighed.Amount of sulphate in the water sample is obtained from the weight is the
precipitate.
BaCl2 + SO42- ------ BaSO4 + 2Cl-
Procedure:-
1. A known volume(v ml) of the water sample is taken in a beaker, heated to boiling and a
warm solution of 5% Barium chloride is added dropwise with constant stirring.
2. A white precipitate of BaSO4 formed, the precipitate is allowed to settle.
3. The precipitate is washed several times with hot water and decanted and finally precipitate is
transferred into the crucible.
4. The crucible containing the precipitate is dried in an oven at 120-130oC and allow the
crucible in a dessicator and weight of the crucible with the precipitate is measured.
5. From the weight of the precipitate(W),the amount of sulphate in the given volume of a water
sample is calculated as:-
233.3 mg of BaSO4 = 96 mg of SO42-
Wt of empty silica crucible = W1 g
Wt of silica crucible + precipate (BaSO4) = W2 g
Wt of BaSO4 Precipate = (W2-W1)g
Amount of sulphate present/lt = (W2-W1) *96 g

233.33 * 1000
= (W2-W1) *96 * 106 ppm

233.33 * 1000
ASSIGNMENT QUESTIONS
1. Explain scale and sludge formation in boilers & mention its ill effects.
2. Define boiler corrosion . Explain boiler corrosion with suitable reactions.
3. Explain the determination of COD of industrial waste water sample.
4. Explain softening of water by Ion exchange process.
5. Define desalination process. Discuss purification of water by Reverse osmosis.
6. Describe secondary treatment of sewage by activated sludge method.
7.Explain the experimental procedure for the determination of fluoride and sulphate ions.

Environmental Pollution
Air pollution is a change in the physical, chemical and biological characteristic of air that causes
adverse effects on humans and other organisms. The substances that are responsible for causing air
pollution are called air pollutants.
1. Types of Air Pollutants:
An air pollutant is known as a substance in the air that can cause harm to humans and the
environment. Pollutants can be in the form of solid particles, liquid droplets, or gases. They can be
natural or man-made. They are classified according to the source of emission into two main groups:
primary and secondary pollutants
A primary pollutant is an air pollutant emitted from a source directly into the atmosphere. The
source can be either a natural process such as sandstorms and volcanic eruptions or anthropogenic
(influenced by humans) such as industrial and vehicle emissions.
Examples of primary pollutants are sulfur dioxide (SO2), carbon monoxide (CO), nitrogen oxides
(NOX), and particulate matter (PM).
A secondary pollutant is an air pollutant formed in the atmosphere as a result of the chemical or the
physical interactions between the primary pollutants themselves or between the primary pollutants
and other atmospheric components. Major examples of secondary pollutants are photochemical
oxidants and secondary particulate matter
Sources of Air Pollution:- Primary air pollutants
Air Pollutant Sources Effects

SO2 volcanoes, anthropogenic resulting Respiratory problems, severe headache,
from the combustion of fuels ,domestic reduced productivity of plants,
burning, thermal power plants, motor yellowing and reduced storage time for
vehicles, different factories like paper paper, yellowing and damage to
mills, fertilizer plants ,steel mills, limestone and marble, damage to
mineral processings etc. leather, increased rate of corrosion of
iron, steel, zinc and aluminium.

NO,NO2 Fossil fuel combustion (gasoline and Forms photochemical smog, at higher
diesel engines) is the main source for concentrations causes leaf damage or
nitrogen oxides in urban areas, while affects the photosynthetic activities of
microbial activity in the soil and plants and causes respiratory problems
agricultural practices such as the use of in mammals.
synthetic fertilizers are its main sources
in rural areas, metallurgical processing
etc.
CO The main sources for atmospheric Affects the respiratory activity as

carbon monoxide are gasoline or diesel- haemoglobin has more affinity for CO
powered engines and biomass burning than for oxygen. Thus, CO combines
(forest fires and biomass fuels) with HB and thus reduces the oxygen-
,incomplete combustion of fuel, carrying capacity of blood. This results
domestic burning, factories, in blurred vision, headache,
metallurgical processes etc. unconsciousness and death due to
asphyxiation (lack of oxygen).
Hydrocarbons Biological process, petroleum Cause swelling of lungs, acute irritation

operations, agricultural activities. to the mucous membrane, carcinogenic
compounds cause cancer.
Lead Lead is used in many industries, lead dust can lead to vomiting bloody
including lead smelting and processing, diarrhoea, nervous problems
the manufacturing of batteries,
pigments, solder, plastics,paint,
ammunition and ceramics, and battery
recycling etc.
Mercury Natural sources of mercury include Mercury can cause kidney problems,
volcanoes, forest fires, cannabar (ore) disorder of cardiac and neurological
and fossil fuels such as coal and problems
petroleum. Levels of mercury in the
environment are increasing due to
discharge from hydroelectric, mining,
pulp, and paper industries.
Particulate Some particulates occur naturally, Smoke causes scarring of lungs,
matters originating from volcanoes, dust storms, irritation .Silica dust can cause
forest and grassland fires, living silicosis,asbestos dust cause asbestosis,
vegetation, and sea spray. Human lead dust can lead to vomiting
activities, such as the burning of fossil bloodydiarrhoea, nervous problems.
fuels in vehicles, power plants and Mercury dust can cause kidney
various industrial processes also problems, disorder of cardiac and
generate significant amounts of neurologival problems.
aerosols.
Secondary air pollutants:-

Ozone:- Ozone is a triatomic oxygen molecules.Ozone forms a protective layer in the stratosphere
which absorbs harmful UV radiations from the sun.The thickness of the ozone layer is about 3mm
and is called Ozonosphere layer.
Formation of Ozone:-Ozone is formed in the stratosphere by the photo dissociation of oxygen

molecule by absorbing UV radiation of 240nm wave length.
O2 -------- 2O
The atomic oxygen combines with molecular oxygen producing Ozone.
O + O2 ------ O3
Ozone dissociates by absorbing UV radiation in the range 200-300nm.
O3 ------ O +O2
Ozone is formed again by the reaction between the products and thus there exists a dynamic
equilibrium between the formation and dissociation of ozone maintaining ozone concentration in the
atmosphere at a constant level.
Effects of UV radiation:- UV radiation causes skin cancer, eye disorders, suppresses the immune
system, decrease in long range agricultural productivity, albumin coagulation, changes in global rain.
Depletion of Ozone layer:-
Compounds emitted from anthropogenic source dissociate ozone into ordinary oxygen and are called
ozone depleting substances. Substances like chlorofluoro carbons used as coolants in refrigeration
and air conditioning are very stable on the earth and slowly drift into stratosphere. They react with
UV radiation to form chlorine free radical which is a ozone depleting species.
CF2Cl2 ------ CF2Cl + Cl
Cl catalyzes the degradation of ozone.
Cl + O3 ----- ClO + O2
ClO + O ------ Cl + O2
The combined effect is O3+ O ------- O2
One CFC molecule can destroy several thousands of ozone.
Control of ozone depletion:-Hydro chlorofluoro carbon(HCFC) and Hydro fluoro alkanes (HFA) are
the alternatives for Chlorofluoro carbon .These compounds are with one or more hydrogen atoms
and undergoes degradation.

Photochemical smog:-
Photochemical smog is due to air stagnation, abundant sunlight and high concentration of
hydrocarbons and oxides of nitrogen in the atmosphere. Higher concentration of NOx and
hydrocarbons are released due to the excess emission rates of automobiles and some stationary
sources. Due to complex photochemical reactions, pollutants such as ozone,aldehydes ,ketones and
PAN are formed.
The main components of photochemical smog are ozone, oxides of nitrogen, hydrogen peroxide,
aldehydes, ketones etc.
How is smog formed?
Below is a simplified explanation of the chemistry of smog formation.

Nitrogen dioxide (NO2) can be broken down by sunlight to form nitric oxide (NO) and an oxygen
radical (O): 1) NO2 + sunlight --- NO + O
Oxygen radicals can then react with atmospheric oxygen (O2) to form ozone (O3):
2) O+ O2 -- O3
Ozone is consumed by nitric oxide to produce nitrogen dioxide and oxygen:
3) O3 + NO ---- NO2 + O2
Harmful products, such as PAN, are produced by reactions of nitrogen dioxide with various
hydrocarbons (R), which are compounds made from carbon, hydrogen and other substances:
4) NO2 + R --- products such as PAN
The main source of these hydrocarbons is the VOCs. Similarly, oxygenated organic and inorganic
compounds (ROx) react with nitric oxide to produce more nitrogen oxides:
5) NO + ROx ---- NO2 + other products
The significance of the presence of the VOCs in these last two reactions is paramount. Ozone is
normally consumed by nitric oxide, as in reaction 3. However, when VOCs are present, nitric oxide
and nitrogen dioxide are consumed as in reactions 4 and 5, allowing the build up of ground level
ozone.
Acid Rain
What is Acid Rain?
Acid rain, or acid deposition, is a term that includes any form of precipitation with acidic
components, such as sulfuric or nitric acid that fall to the ground from the atmosphere in wet or dry
forms. This can include rain, snow, fog, hail or even dust that is acidic.

What Causes Acid Rain?
Acid rain results when sulfur dioxide (SO2) and nitrogen oxides (NOX) are emitted into the
atmosphere and transported by wind and air currents. The SO2 and NOX react with water, oxygen
and other chemicals to form sulfuric and nitric acids. These then mix with water and other materials
before falling to the ground.
While a small portion of the SO2 and NOX that cause acid rain is from natural sources such as
volcanoes, most of it comes from the burning of fossil fuels. The major sources of SO2 and NOX in
the atmosphere are:
 Burning of fossil fuels to generate electricity. Two thirds of SO2 and one fourth of NOX in
the atmosphere come from electric power generators.
 Vehicles and heavy equipment.
 Manufacturing, oil refineries and other industries.
CONTROL OF AIR POLLUTION
1) Control of SO2 Pollutant:-

a) Calsox Process (Lime and Limestone scrubbing):-
In this method the SO2 containg flue gas is passed through the slurry of lime and
limestone. The SO2 reacts with the slurry to form calcium sulfite and calcium sulfate.
These salts are continuously separated from the slurry and discharged into a settling
pond. The remaining solution is recycled to the scrubbing tower, after fresh lime or
limestone are added.
The reaction occurring during this process are :-
CaO + H2O ---- Ca(OH)2
Ca(OH)2 + SO2 --- CaSO3 + H2O
CaCO3 + SO2 ---- CaSO3 + CO2
2CaSO3 + O2 --- 2CaSO4

b) By using ammonia:- SO2 containing gases are passed through ammonia solution, when
ammonium sulphite is obtained as a by-product.
2NH4OH + SO2 ----- (NH4)2SO3 + H2O
2. Control of oxides of Nitrogen, CO and Hydrocarbons:-
Major source of oxides of nitrogen, Carbon monoxide and hydrocarbons is automobile

exhaust. The exhaust emissions from automobiles can be controlled by installing
catalytic converter in the exhaust of the engine. Catalytic converter is a device used to
reduce the toxicity of emissions from an internal combustion engine.
Construction and working of Catalytic converter:-
It consists of a metal casing with two chambers. The exhaust gases (NOx, HC & CO) from
engine pas through two chambers. The first chamber consists of reduction catalyst containing

platinum and Rhodium (Rh) and second chamber consists of oxidation catalyst containing
platinium(Pt) and Palladium (Pd). The metal catalyst supported in form of atomic clusters
over honey comb- like structure made of cordierite. Cordierite is a ceramic material
(magnesium, aluminium silicate) with very high surface area, low thermal coefficient of
expansion and withstand heat upto 1300oC.
The exhaust gases from the engine of a vehicle passes through there two chambers. The
honey comb-like structure allows the hot exhaust gases to move through several parallel
channels and allow gas molecules to come in contact with catalyst. The temperature for
reactions to take place should be higher. The temperature of catalyst chambers will be
maintained at 700oC by hot gases.
Reactions in convertor:- First stage:-
In the first stage catalytic converter involves the use of reduction catalyst like Pt of Rh it
reduces nitrogen oxide to form nitrogen and oxygen.
2NOx ----------------- N2 + X O2
Pt/Rh catalyst
Second stage:-In the second stage the oxidation catalyst reduces the unburnt hydrocarbon
monoxide by burning them over Pt and Pd catalyst to carbon dioxide.
2CO +O2 ---------- 2CO2
CH4 +2O2 ------- CO2 + 2H2O
Third stage:-Incomplete combustion causes soot formation. The carbon soot deposited in the
pores of honey comb is oxidized at operating temperature of the catalyst chamber.
3.Control of Particulate matters :-
Cottrell electrostatic precipitator
It is one of the most widely used device for controlling the particulate matters. Electrostatic
precipitator are mainly installed in the exhaust outlets or chimney of the industrial unit. It
uses the electrical energy directly to remove the particulate matters.
The exhaust gas from the industrial plant carrying the particulate matter like smoke, dust etc,
is passed between metal electrodes maintained at a high potential difference (50000V). The
pointed electrodes develop high intensity current and produce coronas in which the gas
molecules get ionized releasing electrons from the gases. The electrons so generated collide
with the suspended particles present in the gas and the particles become negatively charged.
These negative particles are attracted by the collection electrode. The discharged particles are

removed by tapping or vibrations of the electrode. The particles collect in the conical
collector. Dust-free gas flows out at the top.
Advantage:-
1.Method is of low cost with high collection efficiency.
2.Large quantity of gases can be cleaned.
Disadvantage:- It is applicable for the particulate impurities but not for gaseous impurities.
WASTE MANAGEMENT :-
Solid waste management :

Solid waste management is a process of collecting and treating solid wastes like domestic waste,
industrial waste, mechanical processing waste, waste etc. Solid waste refers to all non-liquid waste
but does not include excreta.
Types of solid waste:-

TYPES OF SOLID WASTE SOURCES
Organic Waste Food stores, domestic , food distribution centers
Combustibles Markets, ware house
Non-combustibles Industries
Municipal waste Street cleaning, waste water treatment plants, landscaping
waste
Dead animals Slaughter areas
Hazardous waste Hospitals and industries
Construction waste Construction areas.
Methods of solid waste management:-

There are different methods of solid waste management. Some of them are:-

Landfilling method:- In a sanitary landfill, garbage is spread out in thin layers, compacted and
covered with clay or plastic foam. In the modern landfills the bottom is covered with an
impermeable liner, usually several layers of clay, thick plastic and sand. The liner protects the
ground water from being contaminated due to percolation of leachate.
Leachate from bottom is pumped and sent for treatment. landfill is full it is covered with clay, sand,
When
gravel and top soil to prevent seepage of water. Several wells are drilled near the landfill site to
monitor if any leakage is contaminating ground water. Methane produced by anaerobic
decomposition is collected and burnt to produce electricity or heat.
Composting:Due to shortage of space for landfill in bigger cities, the biodegradable yard waste
(kept separate from the municipal waste) is allowed to degrade or decompose in a medium. A good
quality nutrient rich and environmental friendly manure is formed which improves the soil
conditions and fertility.
Composting is a biological process in which micro-organisms, mainly fungi and bacteria, convert
degradable organic waste into humus like substance. This finished product, which looks like soil, is
high in carbon and nitrogen and is an excellent medium for growing plants.
Recovery and Recycling:-
Recycling and recovery of resources is the process of taking useful but discarded items for next use.
These items are processed and cleaned before they are recycled. The process aims at reducing energy
loss, consumption of new material and reduction of landfills.
E-waste Management :-
Electronic waste or e-waste describes discarded electrical or electronic devices. Used electronic
goods which cannot be reuse, resale, salvage, recycling, or disposal are also considered e-waste.
Sources:-E-waste encloses ever growing range of unwanted, working electronic devices such as
computers, servers, monitors, TVs, display devices, telecommunication devices such as cellular
phones, batteries and pagers, calculators, audio and video devices, printers, scanners and machines
like refrigerators, air conditioners, microwave oven etc.
Characteristics of e-waste:-
E-wastes that are landfilled produce contaminated leachates which pollute the ground water. Acids
and sludges obtained from melting computer chips, if disposed on the ground causes acidification of
soil.
1. Improperly monitored landfills can cause environmental hazards. Mercury will leach when
certain electronic devices such as circuits breakers which causes health effects include
sensory impairment, dermatitis, memory loss, and muscle weakness. Environmental effects
in animals include death, reduced fertility, and slower growth and development.

2. Lead ions from broken cathode ray tubes gets mixed with acid waters and are common
occurance in landfills. This causes impaired cognitive function, behavioral disturbances,
attention deficits, hyperactivity, and lower IQ. These effects are most damaging to children
whose developing nervous systems are very susceptible to damage caused by lead, cadmium,
and mercury.
3. The most common form of cadmium is found in Nickel-cadmium batteries. When not
properly recycled it can leach into the soil, harming microorganisms and disrupting the soil
ecosystem.
Disposal of e-waste:-
Landfilling:-
This is the most common method of e-waste disposal. Soil is excavated and trenches and made for
burying the e-waste in it. Landfilling is not an environmentally advisable process as e-waste
contains toxic substance like mercury, lead, cadmium etc are released to the soil and the ground
water.
Recycling of e-waste:-
Mobile phones, monitors, CPUs, floppy drives, laptops, keyboards, cables and connecting wires can
be re-utilized with the help of the recycling process. It involves dismantling of the electronic device,
separation of the parts having hazardous substances like PCB,CRT etc and then recovery of the
precious metals like Cu, gold or lead can be done with the help of a e-waste recycler.
Reuse of electronic devices:-

This is the most desirable e-waste recycling process where with slight modifications the mobile
phones, computers, laptops, printers can be reused or given as second hand product.
Biomedical wastes Managements :-

Biomedical waste is any waste produced during the diagnosis, treatment or immunization of human
or animal, research activities pertaining to the production of biological materials.
Sources:-Biomedical wastes is generated from hospitals, clinics, dispensaries, blood banks, animal
house, mortuaries, animal research, labs and veterinary institutions.
Characteristics:-
Biomedical waste management may be contaminated with pathogenic microbes, radioactive
substances, cytotoxic and heavy metals.
They can cause air pollution. The pathogens present in the waste can leach out and contaminate the
groundwater of surface water. Harmful chemicals present in bio-medical waste such as heavy metals
can also cause water pollution. Land pollution is caused by the final disposal of all bio-medical
waste.
Biomedical waste Treatment :-

The goals of biomedical waste treatment are to reduce or eliminate the hazards. Treatment should
render the waste safe for subsequent handling and disposal. There are several treatment method like
incinerator, microwave, autoclave , hydroclave, plasma torch technology,medical waste sterilization
unit.
The above said systems have certain limitations. Heavy metals and plastic cannot be burnt in

incinerators. Microwave cannot take up large pieces of metals and body parts for disinfection.
Final disposal:-
The various disposal options after treatment are incineration, secured landfill, vermicomposting and
public sewers.
Explain environmental pollution, waste management and impurities in water for production of
potable water.
1.Mention the source,ill effects and control of the following atmospheric pollution,
i)oxides of sulphur ii) oxides of nitrogen iii) CO iv)hydrocarbons.
2. Mention the various sources of particulate matters and a method of removing particulate matter
from air.
3.Write a note of acid rain, photochemical smog.
4.Write a note on ozone depletion.
5.What are the sources,effects and control of lead pollution?
6.What are the causes ,effects and disposal method of solid waste,e-waste and biomedical waste?

MODULE 5
INSTRUMENTAL METHODS AND NANOMATERIALS
(CO 5)
Instrumental methods of analysis:-
Theory, Instrumentation and applications of Colorimetry , Flame Photometry ,Atomic Absorption
Spectroscopy, Potentiometry ,Conductometry (Strong acid with strong base, weak acid with a strong
base, mixture of strong acid and a weak acid with a strong base).
NANO MATERIALS:
Introduction,size dependent properties (Surface area,Electrical, Optical,Catalytic and Thermal
properties). Synthesis – bottom up approach (sol-gel, precipitation, & chemical vapour deposition).
Nano scale materials – carbon nano tubes, graphenes & fullerenes-its properties and applications.
Instrumental Methods of analysis

Colorimetric Estimation:-
Theory: Colorimetry is the field of determining the concentration of a coloured compound in a
solution and it is an analytical machine that quantify a solutions concentration by measuring the
absorbance of a specific wavelength of light.
The colorimeter uses the Beer Lambert law . BeerLamberts law is written as: The amount of light
absorbed is directly proportional to the concentration of the solution.
A= €cl, Where, A is the absorbance, € (epsilon) is the molar absorptivity, c is the concentration of
the solution and l is path length ,which is kept constant.
Instrumentation:
Components of the colorimeter:
(a) Light Source: The light source is usually a tungsten lamp for wavelength in the visible range
(320-700 nm). Hydrogen lamp is usually preferred for UV range.
(b) Monochromator: It allows only the required wavelength to pas through it which is followed
by filters
(c) Lens: Used to focus correctly the light from the source through the filter and cuvette to the
detector.
(d) Sample Cuvette: It is a sample holder and for accurate and precise reading cuvette must be
transparent, clean Cuvettes are made of Quartz .
(e) Photosensitive detectors: Detectors detects signal and converting light energy to electrical
energy.
(f) Read out devices: The detector response can be measured by any of the following read out
devices like Galvanometer, ammeter, digital read out.

Application of Colorimetry:-
Ex:- Colorimetric estimation of copper:- When cupric ion react with ammonia, gives a deep-blue
colour which is cuprammonium complex ion.
Cu2+ + 4NH3 ---------- [Cu(NH3)4]2+
Procedure:-
Draw 2,4,6,8,10ml of given copper sulphate solution into separate 50ml volumetric flask. Add 3ml
of ammonia to each of them and also to the unknown solution or test solution of unknown
concentration. Dilute upto the mark with deionized water and mix well. Measure the Absorbance of
these solution using photoelectric colorimeter at 620nm of each of these against the blank solution,
prepared by diluting 3ml of ammonia solution into a 50ml measuring flask with ion exchange water
upto the mark. Plot the graph of absorbance(OD) against conc of copper and determine the
concentration of copper in unknown solution.
Calibration Plot
Applications:
1. Used in quantitative analysis of large numbers of metal ions, organic compounds.
2. Used in photometric titration
3. Determination of composition of the colored complex.

Flame Photometry:-
Theory: A photoelectric flame photometer is a device used in inorganic chemical analysis to

determine the concentration of certain metal ions, among them sodium, potassium, lithium, and
calcium.
The basis of flame photometric working is that, the species of alkali metals (Group 1) and alkaline
earth metals (Group II) metals are dissociated due to the thermal energy provided by the flame
source. Due to this thermal excitation, some of the atoms are excited to a higher energy level .Being
unstable at higher energy level, the atoms falls back to the ground state by emitting some amount of
energy in the form of light radiation. The intensity of the light radiation emitted is proportional to the
concentration of the solution.
Instrumentation:
Parts of a flame photometer
1. Source of flame:
A burner that provides flame and can be maintained in a constant form and at a constant
temperature.
2. Nebuliser and mixing chamber:

Helps to transport the homogeneous solution of the substance into the flame at a steady rate.
3. Optical system (optical filter):

The optical system comprises three parts: convex mirror, lens and filter. The convex mirror
helps to transmit light emitted from the atoms and focus the emissions to the lens. The convex
lens help to focus the light on a point called slit. The reflections from the mirror pass through
the slit and reach the filters..
4. Photo detector:
Detect the emitted light and measure the intensity of radiation emitted by the flame. That is, the
emitted radiation is converted to an electrical signal with the help of photo detector.

Working: The working of the flame photometer involves a series of steps which is discussed in the
following sections.
Nebulisation:
The solution of the substance to be analyzed is first aspirated into the burner, which is then dispersed
into the flame as fine spray particles.
Events occurring in the flame:

Flame photometry employs a variety of fuels mainly air, oxygen or nitrous oxide (N2O) as oxidant.
The temperature of the flame depends on fuel-oxidant ratio.
The various processes in the flame are discussed below:
1.Desolvation: The metal particles in the flame are dehydrated by the flame and hence the solvent is
evaporated.
2.Vapourisation: The metal particles in the sample are dehydrated. This also led to the evaporation
of the solvent.
3.Atomization: Reduction of metal ions in the solvent to metal atoms by the flame heat.
4.Excitation: The electrostatic force of attraction between the electrons and nucleus of the atom
helps them to absorb a particular amount of energy. The atoms then jump to the exited energy state.
Emission process: Since the higher energy state is unstable the atoms jump back to the stable low
energy state with the emission of energy in the form of radiation of characteristic wavelength, which
is measured by the photo detector.
Application:-
Estimation of Sodium ions:-
Draw 1,2,3,4,5cm3 of standard NaCl into 50cm3 of standard flask. Make upto the mark with
deionised water shake well. Adjust compressor pressure to 10psi.On the burner and adjust to get
non-luminous flame. Take distilled water and set the instrument to zero and higher concentration
of NaCl to 100 by using 589nm filter. Now,record the intensity of 1,2,3,4,5cm3 and test
solution.Plot intensity versus volume of NaCl.
Calibration Plot
Atomic absorption spectroscopy (AAS)
Theory:
When a solution is introduced into the flame, the solvent evaporates and vapour of metallic species
is obtained. Some of metal atoms can be raised to an energy level sufficiently high to emit
characteristics radiation of metal-a phenomenon that is used in flame photometry. Here a large
amount of metal atoms remain in non-emitting ground state. When a light of suitable wavelength
passes through a flame, a part of light will be absorbed and this absorption will be proportional to the
intensity of atoms in the flame. So in atomic absorption spectroscopy the amount of light absorbed is
determined because the absorption is proportional to the concentration of the element.
Instrumentation: Parts of an AAS

1. The burner (atomizer): Here the sample from the capillary rises to the tip of burner where it
is burned with the flame produced by the fuel and oxidant combination. The sample after
evaporation leaves a fine residue of neutral atoms.
2. Sample container: This is a beaker-like a container of the sample which is placed below the
burner preferably. A capillary tube drains the sample to the tip of the burner.
3. Fuel and oxidant:.A proper combination of fuels and oxidant are to be used to produce
recommended temperatures. Commonly used fuels include propane, Hydrogen, and acetylene
and oxidants are mostly air or oxygen.
4. Light source (Hollow cathode lamp): The light source should produce a narrow spectrum
with little background noise.
5. Monochromator: This is for the selection of require narrow wave bond.
6. Detector: The detector consists of a photomultiplier tube or simple photocell. The current or
potential recorded for the sample absorption is recorded in computer software and then

analyzed.
Working: When a monochromatic radiation of frequency ν is incident on a molecule, the molecule
in the gaseous state E1 absorbs a photon of energy hν, it undergoes a transition from lower energy
level to higher energy level.
A detector is placed to collect the radiation after interaction with the molecule which shows that
intensity has reduced. With wide range of frequencies, the detector shows the energy has been
absorbed only from the frequency.
ν= (ΔE)/h
Therefore we obtain an absorption spectrum which is defined as a record of the radiation absorbed
by the given sample as a function of wavelength of radiation.
The energy difference between the levels is given as,
ΔE = E2−E1 = hν= hc/λ
Calibration Plot

Applications:
1. Atomic spectroscopy is used for quantitative analysis of metal elements in samples like soil,
plant material.
2. It is especially useful to analyze ionic metal elements in blood, saliva, urine samples like
sodium, potassium, magnesium, calcium and other body fluids.
3. To determine heavy metals like iron, manganese, copper, zinc, mercury, lead, nickel, tin, etc.
in urine, blood, etc. This analysis is essential in case of heavy metal poisoning as regular
monitoring of poison levels in the blood are to be determined until patient recovery.
Potentiometry
Theory: It is an electroanalytical technique in which the amount of a substance in the solution is

determined from emf measurement between two electrodes that are dipped in the analyte solution.
Out of two electrodes one acts as indicator electrode and other acts as reference electrode.
The potential is given by Nernst equation.
Where Eo is the standard potential of the system. As it can be observed from the above equation that
the emf of the solution depends on the concentration of the metal ions in the solution. When titrant is
added to the analyte solution in the beaker the concentration of analyte solution changes and there by
the potential also changes. Initially change in the potential will be small. At equivalence point, there
will be a steep rise in the potential. Beyond the equivalence point there will be no significant change
in potential. The equivalence point is determined by plotting a graph of potential v/s volume of
titrant.
Instrumentation:-

A potentiometer consists of an indicator electrode ,reference electrode and a device for mearusing
the potential. The indicator electrode responds rapidly to the changes in the potential due to change
in the concentration of analyte solution due to addition of titrant from the burette.
Application:-
Determination of FAS by potentiometric method:-
Add one tt of dilute sulphuric acid to the given FAS solution.Immerse the Pt and calomel electroe
assembly in it.Conncet the electrode assembly to a potentiometer and measure the potential.Add
potassium dichromate solution from burette in the increment of 0.5ml,mix well and measure the
potential after each addition. Calculate the normality and amount of ferrous ion in the given solution.
Applications:
1. Analysis of pollutants in water
2. Drug analysis in pharmaceutical industry
3. Food industry for analysis of quality
4. Used in quantitative and qualitative analyses
Conductometry
Theory: Conductometry is the measurement of the electrical conductivity of a solution. The

conductance is defined as the current flow through the conductor. In other words, it is defined as the
reciprocal of the resistance. The unit for the conductance is Seimens (S) which is the reciprocal of
Ohm's (Ω−1). The principle underlying conductometric titrations is the substitutions of ions by other
ions of different mobility , the conductance of a solution depends on the number and mobility of
ions.
Instrumentation
Conductometer consists of a conductivity cell& a conductance measuring device. The cell has 2
platinum electrodes placed at unit distance apart. The assembly responds rapidly to the changes in
the concentration of the analyte. The simple arrangement of conductometric titration is represented
as follows.

Working:
Measurement of conductance can be employed to determine the end point in acid-base titrations. In
conductometric titrations there is a sudden increase in conductance of the solution at equivalence
point.The equivalence point is determined graphically by plotting conductance (ordinate) against titer
values (abscissa). From the equivalence point the concentration of analyte can be determined.
Advantages of conductometric titrations:-
1. Mixture of acids can be titrated more accurately.

2. Colored solutions can be titrated.
3. Very weak acids such as H3PO3, phenol, which cannot be titrated potentiometrically in aqua
solutions, can be titrated conductometric.
Conductometric titration involving strong acid v/s strong base :-
During the titration, for example.of HCl with NaOH, the reaction taking place is:
(H+ + Cl- ) + (Na+ + OH- ) -------- ( Na+ + Cl- ) + H2O
The highly conducting H+ ions initially present in the solution are replaced by the sodium ions having
much smaller ionic conductance,while the concentration of chloride ions remains constant.Therefore,
the conductance first falls and after the equivalence point has been reached,it rapidly rises with further
additions of strong alkali. The two straight lines are obtained and intersection of these two lines give
the end point.
Estimation of HCL
In this titration HCl is taken in the beaker into which electrodes are dipped and standard NaOH
solution from the burette is added in increments of 0.5ml and solution is mixed well and its
conductance is determined. Initially conductance falls till equivalence point due to replacement of
highly mobile H+ ions by less mobile Na+ ions. After equivalence point the conductance increases
rapidly due to increase in the concentration of OH- ions.In the graph of conductance V/S volume of
base,point of intersection of two lines gives the equivalence. The point of intersection of the two

lines gives the volume of NaOH required to neutralize only HCl. (after drawing a perpendicular lines
to x- axis).
Conductometric titration involving weak acid v/s strong base :-

In the titration of a weak acid with a strong base,the shape of the curve depends upon the
concentration and dissociation constant Ka. In the titration of the acetic acid with sodium hydroxide
solution,the salt,sodium acetate,which is formed during the first part of the titration tends to oppose
the ionization of acetic acid still presentand hence the conductance decreases. The rising salt
concentration will,however,tend to increase the conductance of the solution as shown in the figure.
Owing to these opposing influences the titration curves may have minima and its position depends
upon the concentration as well as the strength of the weak acid.
[CH3COO- H+ ] + [Na+ OH-] ----- [CH3COO- Na+ ] + H2O
Conductometric titration involving mixture of strong acid and a weak acid with strong base:-
PROCEDURE:
Pipette out 50cm3 of the given acid mixture into a beaker.Dip the conductivity cell in the solution and
note down the conductance of the solution i.e., when the volume of NaOH added is zero. Now add
standard NaOH solution from a burette in increments of 0. 5cm3. after each addition, stir the solution

gently when the reading is constant, note down the conductance. As the titration proceeds, the
conductance first gradually decreases and this is due to replacement of high mobile H+ ion by low
mobile Na+ ion.Then rises slowly which is due to conversion of weak acid i.e., CH3COOH to its salt
CH3COONa,and finally rises sharply due to presence of free OH - ions. Continue titration until the
conductance is more or less the same as it was in the beginning. Plot a graph of conductance on Y-
axis versus volume of NaOH on X- axis to get three straight lines. The point of intersection of the
first and second lines gives the volume of sodium hydroxide needed to neutralize only hydrochloric
acid.
The point of intersection of the second and third straight lines gives the volume of NaOH required to
neutralize both HCl and CH3COOH (after drawing a perpendicular to X-axis).

NANOMATERIALS
Introduction: This is a term that has entered into the general and scientific vocabulary only recently
but has been used at least as early as 1974 by Taniguchi. Nanotechnology is a multidisciplinary
science and technology and encompasses physical, chemical, biological, engineering and electronic
processes. Nanomaterials are cornerstones of nanoscience and nanotechnology. Nanostructure
science and technology is a broad and interdisciplinary area of research and development activity
that has been growing explosively worldwide in the past few years. It has the potential for
revolutionizing the ways in which materials and products are created and the range and nature of
functionalities that can be accessed. It is already having a significant commercial impact, which will
assuredly increase in the future.
What are nanomaterials?

Nanoscale materials are defined as a set of substances where at least one dimension is
less than approximately 100 nanometers. A nanometer is one billionth of a meter, or 10-9 m
approximately 100,000 times smaller than the diameter of a human hair. Nanomaterials are of
interest because at this scale unique optical, magnetic, electrical, and other properties emerge. These
emergent properties have the potential for great impacts in electronics, medicine, and other fields.
Size dependent properties of Nanomaterials:

Nanomaterials show different physical, chemical, optical, electronic and magnetic properties.
a) Surface properties: Many physical and chemical properties of a material depend on its
surface properties. If a bulk material is subdivided into individual nanomaterials, the total
volume remains same, but the collective surface area greatly increased. Nanomaterials have
significant proportion of atoms existing at the surface. Surface properties are interrelated
with other properties like catalytic activity, gas adsorption and chemical reactivity.
b) Electrical properties: In bulk materials electronic bands are continuous due to overlapping
of orbitals of billions of atoms. But in nanomaterials, very few atoms or molecules present so
that electronic bands becomes separate and the separation between different state varies with
the size of nonmaterial.
c) Optical properties: Optical properties are connected with electronic structure. The discrete
electronic states of nanomaterials allow absorption and emission of light of specific
wavelength. The nanoparticles of different size can scatter radiation of different wavelength.
In addition to that nanoparticles of metals exhibit unique optical properties. Size of metal
nanoparticles is very much less than the wavelength of visible light (400-780 nm). Therefore
metal nanoparticles are not expected to absorb visible light.

d) Thermal properties: As size decreases surface energy increases and melting point
decreases– This is due to the fact that the surface atoms requires less energy to move as they
are in contact with less atoms with the surface.
e) Magnetic effect: Very small particles have special atomic structures with discrete electronic
states which give rise to super- paramagnetism behavior. Magnetic nano-composites find
applications in high density information storage and improved magnetic refrigeration.
f) Catalytic activity: Because of higher surface to volume ratio, nanomaterials exhibit better
catalytic activity. Many nano materials are used as heterogeneous catalysts. Certain nano
structured metal clusters have shown effective catalysis in hydrogenation reactions. They can
be made as electrodes for certain reactions leading to selective product formation
Synthesis of nanomaterials: Bottom up approach

There are two general approaches to the synthesis of nanomaterials and the fabrication of
nanostructures are bottom- up approach and Top-down approach. Principle of Bottom-up
approach is to assemble basic units into larger structure using chemicals or physical forces at the
nanoscale. Bottom approach starts with smaller components which arrange themselves into more
complex assemblies.
Schematic representation of the building up of Nanostructures

Sol- Gel Process:

Sol-gel technique is an important bottom-up approach for the synthesis of nanomaterials.
Sols and gels are types of colloids. A sol is solid particle dispersed in a medium and a gel is a
continuous network of particles with pores filled with liquid.
Starting materials for nanomaterial preparation are called precursors. In sol-gel synthesis
metal salt or metal alkoxide is used as precursor .
A sol is prepared by dissolving precursors (metal alkoxide) in a solvent like alcohol. Sol is
further converted into a gel by hydrolysis and condensation of precursors.
Hydrolysis and condensation reactions are initiated by addition of an acid or base catalyst.
Hydrolysis and condensation reactions is given below
Hydrolysis: M – O – R + H2O → M – OH + R– OH
Condensation: M–OH + M–OH → M – O – M + R – OH

Gel on aging for a known period of time finally nanoscale clusters of metal hydroxides obtained.
Drying of the gel, where water and other volatile liquids are removed from the gel network.
Calcination of the dehydrated gel at temperature up to 800 0C. Resulting in the formation of oxide
which is resistant to rehydration. Then obtained sample is heat treated to get desired
nanoparticles.
The main advantages of sol-gel process are

a) Nanomaterials of high purity can be obtained.
b) Samples can be prepared at lower temperatures.
c) Easy to control synthesis parameters to control physical characteristics like shape and shape of
resulting materials.
Precipitation Method:
Precipitation is normally done by mixing of two reagents to get an insoluble material in the solid
phase which usually settles down in the reaction vessel. The particles of the precipitate have mm to

µm size. Precipitation method can be used to prepare nanoparticles of metal oxides, metal
sulphides and metals.
1. The precipitation technique of preparation of nano materials involves two steps

nucleation and (ii) growth of nuclei to form a particle.
2. In this method, an inorganic metal salt (such as nitrate, chloride or acetate of metal)
is dissolved in water ( precursor solution) resulting to form metal hydrate.
3. When precipitating agents like NaOH, NH4OH or Na2CO3 is added to metal
hydrates, nucleus formation is initiated.
4. The concentration of the solution increase and reaches super saturation, nucleus
further grows into particles, which gets precipitated.
5. The product obtained is filtered, washed with water, air dried. The dried powder on
subsequent calcinations to obtain the final crystalline metal oxide.
Advantages:
1. The process is relatively economical.
2. Wide range of single and multi components of oxide nano powders can be synthesized.
Disadvantages:
1. Inability to control the size of the particles.
2. Chances of aggregation of nano particles.
Chemical Vapour condensation:

In this method nanoparticles are synthesized from the gaseous phase by a chemical
reaction or decomposition of precursors at high temperature.
1. In Chemical vapour condensation technique precursor material is heated by passing

through hot surface resulting in vaporization of material.
2. The method consists in passing an inert gas through a chamber consisting of
precursor liquid and the vapours are delivered to a hot wall reactor. Vapour
decomposes in the hot zone and form particle which is deposited over the substrate.
The particles are scraped into a collector at regulated intervals.
3. The material settled on the surface of the cold finger is removed by scrapping
4. The thickness and size of the nano material to be formed is controlled by adjusting
the flow rate of the carrier gas swiping the reactants.

Advantages:
1. This is relatively simple technique.
2. By this method, it is possible to deposit nanomaterials with almost any size and shape.
3. The bi products and leftovers from the reactions are cleanly removed to the gas phase.
So product obtained is highly pure.
Nano scale materials:

Materials made of nanoparticles are called nanoscale materials. Nanomaterials are
finding the applications in the field of medical diagnostics, health care, environmental
remediation, high density data storage etc. These have change in physiochemical properties
such as band gap, melting point, magnetic properties and specific heat and shape.
Carbon nano tubes:
A carbon nano tube is a tubular structure made up of carbon atoms, having diameter of
nanometer order but length in micrometers. They are also called as bucky tubes –they
posses extraordinary strength and electrical and thermal properties. Carbon nano tubes are
related to fullerenes and is regarded as another allotrope of carbon. Fullerenes are spherical
and carbon nano tubes are cylindrical.
Types of carbon nanotubes
1. Single walled nanotubes(SWNT’s)

Which is of diameter approximately 1nm and with tube length several million times longer
The structure of SWNT’s is imagined to be a wrapping of one atom thick layer of graphite
into a cylindrical shape.

2. Multi Walled nanotubes (MWNT’s)

Consists of multiple rolled layers carbon – sheets of graphite are arranged in concentric
cylindrical form.
Synthesis of carbon nano tubes:

1. Chemical vapour deposition is suitable method for producing carbon nano tubes.
2. The process involves passing a hydrocarbon vapour over a catalyst as Fe, Co, Ni, or Pt
kept in a tubular furnace at high temperature to decompose the hydrocarbon into carbon
and hydrogen.
3. Depending on the hydrocarbon precursor, the temperature used in the range of 600 -
1200˚C .
4. An inert gas is also passed and carbon nano tubes grow on the catalyst surface and are
collected after cooling the furnace.
5. Usually methane, ethylene, acetylene and CO gases are used as precursors for carbon
nano tubes.
Properties and applications of carbon nano tubes:
1. Nano tubes are cylindrical carbon molecules exhibits physical and chemical properties ,
which are valuable for nanotechnology, electronics, optics and material science and
technology.
2. Carbon nano tubes exhibit high electrical conductivity and also high thermal
conductivity. They have low density and very high mechanical strength.
3. These can emit electrons when subjected to a high electric field .Due to this property
they are used in field emission X-ray tubes.
4. Single wall nano tubes are used in solar panels and these are used to store hydrogen to
be used as a fuel source.
5. Single wall carbon nano tubes are efficiently absorb radiation in the near IR range (700-
1100 nm) and convert it to heat. This property is used in cancer thermotherapy to
selectively kill cancer cells.

Fullerenes:
1. A fullerene composed entirely of carbon atoms, in the form of a hollow sphere,

ellipsoid, tube and many other shapes. Spherical fullerenes are also called
buckyballs, and they resemble the balls used in football (soccer).
2. One of the allotrope of carbon is carbon-60 molecule with 60 atoms arranged
spherically. This was called fullerene.
3. The discovery of fullerenes greatly expanded the number of known carbon
allotropes. Minute quantities of the fullerenes in the form of C60, C70, C76, C82 and
C84 etc carbon atoms arranged spherically.
Production of fullerenes: Fullerenes are produced by creating an electric arc between

carbon or graphite electrodes in an inert gas atmosphere. Electric arc liberates a black
powder in the form of a soot. 10% of the soot is made up of C60 . The fullerenes in the
soot are then extracted by solvent like toluene. Then the solvent is removed and a solid
mixture of C60 with small amounts of large fullerenes. Its particle size of about 2 nm.
Characteristics of Fullerenes
1. An important characteristic of C60 molecule is its high symmetry with 120

symmetry operations. Each carbon bond with three other carbon atoms using sp2
hybridization
2. Chemically fullerens stable breaking the balls requires a temperature above 1000oC,
However fullerens are quite reactive as they possess π electrons.
3. Fullerens are insoluble in water, sparingly soluble in many other solvents and more
soluble in toluene and carbon disulphide.
4. Fullerens themselves are non toxic but some of their derivatives are toxic.
Applications:
1. Fullerenes are promising components of future microelectrical systems and in
nanotechnology.
2. Fullerenes can be made to be magnetic, acts as superconductors, serve as a

lubricant, or absorb light.

3. Many recent applications of fullerenes include medical applications, superconductors and fibre
optics.
4. It is used as lubricants, adhesives, charge transfer complexes, cosmetics, catalyst etc.
5. It is used as electrode material in secondary batteries, non aqueous batteries and as hydrogen
storage material for fuel cell electrodes.
Graphenes:-
Graphene is an allotrope (form) of carbon consisting of a single layer of carbon atoms arranged in
a hexagonal lattice.
Properties:- It is allotropes of carbon in the form of a plane of sp2 bonded atoms with the
molecular bond length of 0.142 nanometers. Layers of grapheme stacked on top of each other form
graphite with an interplanar spacing of 0.335nanometers. The separate layers of grapheme in
graphite are held together by vander waals forces. It is the lightest material and the strongest
compound discovered. It is the best conductor of heat at room temperature and an excellent
conductor of electricity. It is an extremely diverse material and can be combined with other
elements to produce different materials with various superior properties.
Applications:- Touchscreen, transistor, computer chips, batteries, energy generation,
supercapacitors solar cells etc.
Course Outcomes: Upon successful completion of this course, students will be able to:
Illustrate different techniques of instrumental methods of analysis and synthesis, properties and
applications of nano materials.

ASSIGNMENT QUESTIONS
1.Explain the theory, instrumentation and applications of flame photometry
2.Explain the theory and instrumentation of conductometry.
3.Explain the theory and instrumentation of potentiometry and colorimetry.
4.Explain the theory,instrumentation and application of atomic absorption spectroscopy.

5. Explain the synthesis of nano materials by Sol- gel method.
6. Explain the synthesis of nano materials by precipitation process.
3. Discuss chemical vapour condensation process.
4. Write short note on Carbon nano tubes & Graphenes.
5. Explain fullerences & mention its advantages.
6. What are nano materials and explain any four size dependent propert ies of a nano materials.

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GLOBAL ACADEMY OF TECHNOLOGY

IDEAL HOMES TOWNSHIP, RAJARAJESHWARINAGAR, OFF MYSORE ROAD,

SEMESTER: I / II SUBJECT CODE: 18CHE12/22

Dr. N SUMA , Dr. ASHOK S D ,Mr. ADARSHA J R ,Mr. BHASKAR M,

DEPARTMENT OF SCIENCES AND HUMANITIES

To be an education provider in science and humanities with emphasis on excellence

 Impart fundamental knowledge in science for understanding advancements in

Subject Name Engineering Chemistry No. of Sessions 50

Total Number of Sessions 50

3. Design/development of solutions: Design solutions for complex engineering problems and

4. Conduct investigations of complex problems: Use research-based knowledge and research

7. Environment and sustainability: Understand the impact of the professional engineering

10. Communication: Communicate effectively on complex engineering activities with the

Global Academy of Technology, RR nagar , Bengaluru 4

Global Academy of Technology, RR nagar , Bengaluru 5

Entropy: It is the measure of disorderness or randomness of a system.The entropy change

Single Electrode Potential

∆G = -nFE --------------- (1)

∆G =∆G0+ RTlnK ------------- (3)

Substitute the value of K in equation (3)

Global Academy of Technology, RR nagar , Bengaluru 6

Substitute from equ (1) and (2) for ∆G and ∆G0

-nFE = -nFE0+ RT ln [M]- RT ln[Mn+]

Divide throughout by -nF

Under standard conditions M=1, hence the above equation becomes (

Substituting the values of R = 8.314 JK-1mol-1, F = 96,500 C mol-1, T = 250C.

E = E0 + 0.0591 log [Mn+]

Global Academy of Technology, RR nagar , Bengaluru 7

The cell is represented as Hg / Hg2Cl2 / Cl-

2Hg + 2Cl- Equilibrium reaction: Hg2Cl2 + 2e- ↔ 2Hg

The electrode potential is given by,

Advantages of Calomel elctrode:

Global Academy of Technology, RR nagar , Bengaluru 8

When dipped in a solution it can be represented as

EG = E0G + 0.0591 log (H+)

Determination of pH by using glass electrode:-

Global Academy of Technology, RR nagar , Bengaluru 9

The cell assembly is represented as

The PH is determined by using following relation,

Ecell = EGlass - Ecalomel .............. (1)

Ecell = E0G –0.0591pH- Ecalomel

pH = E0G –Ecalomel -Ecell

E = 0.0591 log [C2 ]

Ex:- Zinc concentration cell:-

Global Academy of Technology, RR nagar , Bengaluru 10

Cell can be represented as Zn/Zn2+ (C1) // Zn2+ (C2)/Zn

Numerical Problems:- ( Concentration cell)

E = 0.0591/n log [C2 / C1]

2.The spontaneous galvanic cell tin|tin ion (0.024M)||tin ion(0.064M)|tin develops a

Ecell= 0.0591/n log[C2]/[ C1]

3.Two copper rods placed in copper sulphate solutions to form a concentration

Global Academy of Technology, RR nagar , Bengaluru 11

Ecell = 0.0591/n log[C2]/[ C1]

4. The emf of the cell Cu/CuSO4(0.01M)//CuSO4(xM)/Cu is 0.0295V at 25°C.Find the

Numerical :- (Electrode Potential using Nernst equation)

E = E0 + 0.0591 log [Cathodic species]

= -0.40 –(-1.18) =0.78V

Global Academy of Technology, RR nagar , Bengaluru 12

E = E0 + 0.0591 log [Cathodic species] n