Types of Titration
Types of Titration
Types of Titration
The word "titration" comes from the Latin "titalus," meaning inscription or
title. The French word, titre, also comes from this origin, meaning rank is a common
laboratory method of quantitative/chemical analysis that can be used to determine the
concentration of a known reactant (analyte). The basis of the method is a chemical
reaction of a standard solution (titrant) with a solution of an analyte.
The analyte (A) is a solution of the substance whose concentration is unknown and sought
in the analysis. The titrant (T) is a solution in which the concentration of a solute is
precisely known. Because volume measurements play a key role in titration, it is also
known as volumetric analysis. Usually it is the volume of the titrant required to react with
a given quantity of an analyte that is precisely determined during a titration.
Basics of titration
Equipments used :
♦ Buret,(is a cylindrical tube with a stopcock at one end).
♦ Pipette: Delivers an accurate volume of a solution. Often this is 25 cm3.
♦ Volumetric flask:Used to make up an accurate volume of a solution, for example,
250 cm3. This could be a standard solution (of exactly known concentration and
known solute).
♦ Ph meter
♦ Indicators : provide some visual clue that the reaction is complete.
Titration Notes:
♦ Always rinse buret with water (from a beaker, not the faucet) first. Second, rinse
with a small amount of the titrant and drain it through the tip.
♦ Fill the buret with the titrant using a funnel.
♦ Fill the buret tip by momentarily opening the stopcock.
♦ Now you are ready to read the initial volume (bottom of the meniscus).
Remember that burets are graduated in a downward direction. The first estimated
digit will probably be the hundredths place.
♦ Do not waste time trying to fill the buret to zero for each titration.
♦ Do not start above the 0 mL mark or titrate past the 50 mL mark.
♦ Always use white paper underneath your sample flask so that you will notice
slight color changes.
♦ Learn to swirl the flask without removing it from underneath the buret.
♦ Use a drop, drop, drop pace until you see the color change becoming more than
local (where the titrant meets the sample). Now proceed dropwise.
♦ Second and third trial titrations should always be fast assuming the sample will
be about the same because you now know approximately how much titrant is
needed. If the first titration required 25 mL than you can add 22 mL all at once
and then proceed cautiously.
♦ Remember that the amount of water used to dilute the sample is not crucial
because it does not affect "how many" of the sample molecules are present in the
sample flask. Diluting with water allows you to see the color change easier.
♦ Always label multiple burets and sample flasks.
♦ Remember to add indicator.
Types of titration:
Titration Reaction types
1) Acid-Base Titrations
2) Redox titrations
3) Complexometric Titrations
4) Zeta- potential Tittrations
5) Miscellaneous titration
6) Iodimetry titration
7) Precipitation titration
8) KjeldahlTitration
9) Argentometric Titrations
9.1) The Mohr titration:
9.2) Volhard titration
9.3) Fajans titration
10) Classification of titration by end-point techniques
10.1) Conductometric titration
10.2) Potentiometric titration
10.3) Spectrophotometric titration
10.4) Amperometric titration
10.5) Thermometric or enthalpimetric titration
10.6) Nonaqueous titration
10.7) Automatic titration
10.8) electrochemical titration
11)Back titrations
12) Virus titration
Titrimatery types:
1) volumetric titrimetry
2) gravimetric or weight titrimetry
3) coulometrictitrimetry
4) standardization
1) Acid-Base Titrations:
Titration is a process of neutralization whereby a titrant (a solution
of known concentration) is delivered into an analyte (unknown solution) until the
unknown solution is completely neutralized. This will allow information about the
unknown solution to be determined. An indicator is (often) a weak acid that is placed
into the unknown solution to determine the endpoint of the titration (the pH at which the
indicator changes color). The equivalence point of the titration is the point when the
moles of H+ are equal to the moles of OH- in a titration. The progress of an acid-base
titration is often monitored by plotting the pH of the solution being analyzed as a function
of the amount of titrant added. The graph produced is called a titration curve.
*Note: weak acid / weak base titrations are too complicated and are almost never carried
out.
Example:
In titration, one solution (solution #1) is added to another solution (solution #2) until a
chemical reaction between the components in the solutions has run to completion.
Solution #1 is called the titrant, and we say that it is used to titrate solution #2. The
completion of reaction is usually shown by a change of color caused
by a substance called an indicator.
A typical titration proceeds in the following way. A specific volume
of the solution to be titrated (solution #2) is poured into an
Erlenmeyer flask (Figure 1). For example, 25.00 mL of a nitric acid
solution of unknown concentration might be added to a 250 mL
Erlenmeyer flask.
A solution of a substance that reacts with the solute in solution #2 is
added to a buret. This solution in the buret, which has a known
concentration, is the titrant. The buret is set up over the Erlenmeyer
flask so the titrant can be added in a controlled manner to the
solution to be titrated (Figure 1). For example, a 0.115 M NaOH
solution might be added to a buret, which is set up over the
Erlenmeyer flask containing the nitric acid solution.
An indicator is added to the solution being titrated.In our example,
phenolphthalein, which is a commonly used acid-base indicator, is
added to the nitric acid solution in the Erlenmeyer flask.
Phenolphthalein has two chemical forms. In acidic conditions, it is in
the acid form, which is colorless. In basic conditions, an H+ ion is
removed from each phenolphthalein molecule, converting it to its
base form, which is red.
The titrant is slowly added to the solution being titrated until the indicator changes color,
showing that the reaction is complete. This stage in the procedure is called the endpoint.
In our example, the NaOH solution is slowly added from the buret until the mixture in the
Erlenmeyer flask changes from colorless to red. The OH- ions in the NaOH solution react
with the H3O+ ions in the HNO3 solution.
= or 0.0842 M HNO3
The first step the dimensional analysis thought-process is to clearly identify the units that
you want. Molarity describes the number of moles of solute per liter of solution, so we
start by placing moles of HNO3 over 1 L HNO3 solution.
Because molarity is a ratio of two units, we begin our calculation with a ratio of two
units. Knowing that we want volume of HNO3 solution on the bottom when we are done,
we place 25.00 mL HNO3 solution on the bottom at the start. We place 18.3 mL NaOH
solution on the top of our ratio, giving us the ratio of two units overall that we want.
We convert milliliters of HNO3 solution to liters of HNO3 solution using the relationship
between milliliters and liters to convert milliliters. The last two conversion factors
convert from amount of one substance in a chemical reaction (mL NaOH solution) to
amount of another substance in the reaction (mol HNO3). Thus, this is an equation
stoichiometry problem that requires at its core the conversion of moles of NaOH to moles
of HNO3 using the molar ratio for the reaction between them.
In order to use the molar ratio to convert from moles of NaOH to moles of HNO3, we
need to convert from volume of NaOH solution to moles of NaOH using the molarity as a
conversion factor.
Applications of acid-base titration:
In the determination of iron in pharmaceutical preparations
First of all, acid-base titration, to control acidity or alkilinity of solutions, to
do neutralisation tests and analyze mixtures of acids
Wide use is in titration processes
2) Red-ox titrartion:
Titration of a reducing agent by an oxidizing agent or titration of an oxidizing
agent by a reducing agent. The concentrations of redox-active species can be determined
by redox titrations. In a redox titration, a measured sample of the unknown is titrated
against a standard solution of a substance that will oxidize or reduce the unknown.
Red-ox reaction:
A redox reaction (reduction and oxidation reaction) is a reaction in which there is
a transfer of electrons. When an element is reduced, it gains electrons and its oxidation
number is reduced. When an element is oxidized, it loses electrons and its oxidation
number increases. Reduction and oxidation always happen at the same time
A REDOX titration is a volumetric method that relies on the oxidation of the analyte
(substance to be analysed).
The titrant (solution of known concentration) is often an oxidising agent.
6) Iodimetry titration:
Iodometry is a method of volumetric chemical analysis, a titration
where the appearance or disappearance of elementary iodine indicates the end point.
Usual reagents are sodium thiosulfate as titrant, starch as an indicator (it forms blue
complex with iodine molecules - though polyvinyl alcohol has started to be used recently
as well), and an iodine compound (iodide or iodate, depending on the desired reaction
with the sample).
The principal reaction is the reduction of iodine to iodide by thiosulfate:
I2 + 2 S2O32− → S4O62− + 2 I−
Application of iodiometry titration:
A common and illustrative use of iodometry is the measurement of concentration
of chlorine in water. Chlorine in pH under 8 oxidizes iodide to iodine. An
overabundance of potassium iodide is added to the known amount of sample in
acidic environment (pH < 4, the reaction is not complete in more alkaline pH).
Starch is added, forming a blue clathrate complex with the liberated iodine. The
blue solution is then titrated with thiosulfate until the blue color vanishes.
Determination of Vit-C (ascorbic acid) in fruit juices by Iodimetric method
Analysis of commercial Hypochlorite solution lodometrically.
Analysis of hydrogen peroxide Iodometrically.
9) Argentometric Titrations:
Titrimetric methods based on silver nitrate are sometimes called
argentometric methods.
the Volhard titration involves the addition of excess silver nitrate to the analyte;
the silver chloride is filtered, and the remaining silver nitrate is titrated against
thiocyanate,[1] with iron(III) as an indicator which forms blood-red
[Fe(OH2)5(SCN)]2+ at the end point:
Ag+ (aq) + SCN− (aq) → AgSCN (s) (Ksp = 1.16 × 10−12)
Fe(OH)(OH2)52+ (aq) + SCN− (aq)→ [Fe(OH2)5(SCN)]2+ + OH−
Titrimetry types:
Titrimetry: measuring the quantity of a reagent of known conc required to react with a
measured quantity of sample of an unknown con.
(i) Volumetric Titrimetry
involves measuring the volume of a solution of
known concentration that is needed to react essentially completely with the analyte.
(ii) Gravimetric Titrimetry
differ only in that the mass of the reagent is measured
instead of its volume.
(iii) Coulometric Titrimetry: The reagent is a constant direct electrical current of
known magnitude that consumes the analyte the time required and thus the total
charge to complete the electrochemical reaction is measured.
pX = -log10[X]
♦ http://en.wikipedia.org/wiki/Titration
♦ CHM 286 lecture, March 16, 2009 Harris Ch. 6 (6-1 – 6-4; 6-6)
♦ http://www.dartmouth.edu/~chemlab/techniques/titration.html
♦ http://www.bcpl.net/~kdrews/titration/page4.html
♦ Kirtikar K.R. and Basu B.D., Morus Linn, Indian,Medicinal Plants,
2nd edition,Periodical Experts,Books Agency, New Delhi, Vol. 3,
1991, 2308.
♦ CSIR, Morus Linn, The wealth of India: Raw,materials, Publication
and Information
Directorate, New Delhi, Vol. VI, 1962, 429-436.
♦ http://www.dartmouth.edu/~chemlab/techniques/titration.html
♦ http://www.britannica.com/EBchecked/topic/597325/titration
♦ http://www.microcal.com/technology/itc.asp
♦ Performing a Titration ,Supplemental Lab Handout ,CHM2260
♦ http://www.itmonline.org/arts/morus.htm
♦ Nadkarni K.M., Vegetable kingdom, Indian,Materia Medica, 3rd
edition, Popular,Prakashan,Pvt. Ltd. , Bomaby, Vol. 1, 1991
(reprint), 816-817.
♦ www.creative-chemistry.org.uk/alevel/module5/.../N-ch5-03.pdf
♦ http://www.answers.com/topic/redox-titration
♦ http://www.drbateman.net/asa2sums/sum3.1B/burette.jpg
♦ http://www.bioquest.org/icbl/projectfiles/titration.jpg
http://www.chem.iastate.edu/group/Greenbowe/sections/projectfolder
/flashfiles/redoxNew/redox.html
♦ http://ull.chemistry.uakron.edu/analytical/REDOX_titrations/
Contents
Introduction
Basics of titration
Equipment used
Indicators for titration
Standard method of titration
Titration with ph meter
Titration notes
Types of titration
Titration Reaction types
i. Acid-Base Titrations
ii. Redox titrations
iii. Complexometric Titrations
iv. Zeta- potential Tittrations
v. Miscellaneous titration
vi. Iodimetry titration
vii. Precipitation titration
viii. KjeldahlTitration
ix. Argentometric Titrations
The Mohr titration:
Volhard titration
Fajans titration
x. Classification of titration by end-point techniques
Conductometric titration
Potentiometric titration
Spectrophotometric titration
Amperometric titration
Thermometric or enthalpimetric titration
Nonaqueous titration
Automatic titration
Electrochemical titration
xi. Back titrations
xii. Virus titration
Titrimatery types:
i. volumetric titrimetry
ii. gravimetric or weight titrimetry
iii. coulometric titrimetry
iv. standardized
Types of Titration Curves:
Sigmoidal curve:
Linear segment curve:
Refrences