Acids, Bases & Salts

ACIDS, BASES & SALTS
PREPARED BY: NADINE ELLIS-HALL

OBJECTIVES
 define acid, acid anhydride, base, alkali, salt,
acidic, basic, amphoteric and neutral oxides
 relate acidity and alkalinity to the pH scale
 discuss the strength of acids and alkalis on

the basis of their completeness of ionisation
 investigate the reactions of non oxidising

acids
OBJECTIVES
 list examples of acids in living systems
 investigate the reaction of bases with

ammonium salts
 identify an appropriate method of salt

preparation based on the solubility of the salt
 list the uses and dangers of salts

OBJECTIVES
 distinguish between acid salts and normal
salts
 Investigate neutralisation reactions using

indicators and temperature changes
 perform calculations using volumetric

analysis data
ACID-DEFINITION
 An acid is a proton (H+) donor
 An acid is a substance which produces

hydrogen ions in solution
 An Acid Anhydride is a compound that forms

an acid when it reacts with water, eg. Carbon
dioxide and sulphur dioxide.
ACID- PROPERTIES
 Acids have a sour taste
 Acids turn litmus paper and solution red
 All acids contain hydrogen ions as the only

positively charged ion
- HCl H+ + Cl-
- H2SO4 2H+ + SO42-
- H3PO4 3H+ + PO43-
ACID – PROPERTIES CONT’D
 Most acids react with most metals to produce
a salt and hydrogen gas.
- Mg(s) + 2HCl(aq) MgCl2(aq) + H2(g)
- Hydrogen gas can be tested for using a lit

splint which goes out with a popping sound
( a small explosion).
 Acids neutralise bases producing a salt and
water
- CuO(s) + H2SO4(aq) CuSO4(aq) + H2O(l)
- NaOH(aq) + HCl(aq) NaCl(aq) + H2O(l)

 Acids reacts with carbonates and hydrogen
carbonates producing salts, water & carbon
dioxide
- CaCO3(s) + 2HCl(aq) CaCl2(aq) + H2O(l)
+ CO2(g)
- NaHCO3(s) + HCl(aq) NaCl(aq) + H2O(l) +

CO2(g)
Basicity of an acid
 The basicity of an acid is the number of
moles of hydrogen ions produced when 1
mole of the acid is dissolved in water. Acids
can be monobasic, dibasic or tribasic.
 HCl H+ + Cl-
(aq)
 H2SO4(aq) 2H+(aq) + SO42-(aq)
 H3PO4(aq) 3H+(aq) + PO43-(aq)
Common acids
 Ethanoic acid/Acetic acid – vinegar
 Methanoic acid – ants sting
 Citric acid – citrus friuts eg. Lime
 Hydrochloric acid – stomach
 Lactic acid – sour milk

Common acids used in the lab
 Hydrochloric acid
 Nitric acid
 Sulphuric acid
 Ethanoic acid
 Phosphoric acid
Concentration vs Strength
 Concentration is the amount of solute
dissolved in a specified volume of solution
 Strength is the degree of ionisation or

dissociation of acid molecules in solution.
- Strong acid or base dissociates or ionises

completely or almost completely in solution.
- Weak acid or base partially dissociates or
ionises in solution.
Strong and weak acid & base
examples
 Strong
- Acid
- HCl(aq) H+(aq) + Cl-(aq)
- Base
- NaOH(aq) Na+(aq) + OH-(aq)
Weak
- Acid
- CH COOH H+(aq) + CH3COO-(aq)

3 (aq)
- Base
- NH4OH(aq) NH4+(aq) + OH-(aq)
Indicators & pH
 The pH scale is a scale of numbers from 0 to
14
- pH below 7 is acidic
- pH of 7 is neutral
- pH above 7 is alkaline
An indicator is a substance which exhibits

different colour species in acidic and alkaline
media.
Examples of indicators
Indicator Colour in acid Colour in alkali
Methyl orange red yellow
Phenolphthalein colourless pink
Bromothymol blue yellow blue
Litmus red blue

Base- Definition
 A base is defined as substance which
combines with hydrogen ions
- Bases are usually oxides and hydroxides of
metals
- Soluble bases are called alkalis, the
hydroxides of group 1 metals and ammonium
are alkalis.
Bases - Properties
 Alkalis are soapy to touch as they react with
the natural oils in the skin to form soap.
 Alkalis turn litmus blue
 Bases contain hydroxide ions or oxide ions
- CuO Cu2+ + O2-
- NaOH Na+ + OH-
- All alkalis are soluble in water and give

solutions which contain hydroxide ions.
Bases-Properties Cont’d
 Alkalis will often react with salt solutions to
form insoluble precipitates.
- When a solid is formed by the reaction of

solutions, the solid is called a precipitate.
- CuSO4(aq) + 2NaOH(aq) Cu(OH)2(s)

+Na2SO4(aq)
Bases-Properties Cont’d
 Bases neutralise acids to form salt and water
 Alkalis react with some metals to produce a

salt and hydrogen gas
- Zn(s) + 2NaOH(aq) Na2ZnO2(aq) +H2(g)

Common Bases
 Sodium hydroxide
 Potassium hydroxide
 Calcium hydroxide
 Zinc oxide
 Copper(II) oxide
 Iron(III) oxide
Salts - Definition
 A salt is a compound which is made up of
positive metallic ions or ammonium ions
derived from a basic oxide/hydroxide and an
anion derived from an acid.
 A salt is formed when metallic or ammonium

ions replace the hydrogen ion/s in an acid.
Classes of Salts
 Normal salts- these are formed when all
hydrogen ions in an acid are replaced by
metallic or ammonium ions
 Acid salts – these are formed when some of the

hydrogen ions in a dibasic or tribasic acid are
replaced by metallic or ammonium ions
 Basic salts – these are salts which contain oxide

or hydroxide ions, metallic or ammonium ions
and an anion from an acid.
Examples of classes of salts
 Normal salt
- Sodium chloride - NaCl
- Sodium phosphate - Na3PO4
Acid salt
- Disodium hydrogenphosphate - Na HPO
2 4
- Sodium dihydrogenphospate – NaH2PO4
Basic salt
- Basic zinc chloride – Zn(OH)Cl
Salts Cont’d
 Double salts – This is formed when the
solution of two salts are mixed together and
a new salt with a new colour and shape is
formed.
- Eg. Iron(II) ammonium sulphate –

FeSO4(NH4)2SO4.6H2O
- In solution this produces iron(II) ions,
ammonium ions and sulphate ions.
Water of crystallisation
 Some salts contain a fixed amount of water
within their crystals. This water is trapped
during the formation of the crystals and in
many instances determine the shape and
colour of the crystals.
 CuSO4.5H2O
Preparation of salts
 There are several methods used to prepare
salts in the lab. The method chosen is
dependent on the properties of salt.
 Insoluble salts are prepared by ionic

precipitation. This is carried out by mixing
solutions containing the ions required.
 2KI
(aq) + Pb(NO3)2(aq) PbI2(s) + 2KNO3(aq)
Preparation of salts cont’d
 Anhydrous salt (No water of crystallisation)
are prepared using the direct synthesis
method.
 The elements which make up a compound are

combined together directly
 2Fe + 3Cl 2FeCl3(s)
(s) 2(g)
Preparation of salts cont’d
 Soluble salts can be prepared by four (4) main
methods:
- Metal and an acid
- Insoluble base and an acid
- Carbonate and an acid
- Alkali and an acid
Steps to prepare salts
 These steps can be used when utilising an
acid and metal or insoluble base or
carbonates.
- Measure a specified volume of acid
- Add small amounts of the solid until no more
will react
- Filter to remove excess solid and discard
residue
- Heat the filtrate until the first crystal appears,
allow to stand until crystals form.
TYPES OF OXIDES
 Acidic – produces an acidic solution mainly non-
metallic oxides eg. SO3
 Basic – produces an alkaline solution mainly

metallic oxides eg. Na2O
 Amphoteric – reacts with both acids and alkalis

eg. Al2O3
 Neutral – does not react with either acids or

alkalis eg. CO

Acids, Bases & Salts

Uploaded by

Copyright:

Available Formats

Acids, Bases & Salts

Uploaded by

Document Information

Original Description:

Copyright

Available Formats

Share this document

Share or Embed Document

Sharing Options

Did you find this document useful?

Is this content inappropriate?

Copyright:

Available Formats

Acids, Bases & Salts

Uploaded by

Copyright:

Available Formats

ACIDS, BASES & SALTS

PREPARED BY: NADINE ELLIS-HALL

 relate acidity and alkalinity to the pH scale

 discuss the strength of acids and alkalis on

 investigate the reactions of non oxidising

 investigate the reaction of bases with

 identify an appropriate method of salt

 list the uses and dangers of salts

 Investigate neutralisation reactions using

 perform calculations using volumetric

 An acid is a substance which produces

 An Acid Anhydride is a compound that forms

 Acids turn litmus paper and solution red

 All acids contain hydrogen ions as the only

- Mg(s) + 2HCl(aq) MgCl2(aq) + H2(g)

- Hydrogen gas can be tested for using a lit

- CuO(s) + H2SO4(aq) CuSO4(aq) + H2O(l)

- NaOH(aq) + HCl(aq) NaCl(aq) + H2O(l)

- NaHCO3(s) + HCl(aq) NaCl(aq) + H2O(l) +

 Methanoic acid – ants sting

 Citric acid – citrus friuts eg. Lime

 Hydrochloric acid – stomach

 Lactic acid – sour milk

 Strength is the degree of ionisation or

- Strong acid or base dissociates or ionises

- CH COOH H+(aq) + CH3COO-(aq)

An indicator is a substance which exhibits

Methyl orange red yellow

Phenolphthalein colourless pink

Bromothymol blue yellow blue

Litmus red blue

- All alkalis are soluble in water and give

- When a solid is formed by the reaction of

- CuSO4(aq) + 2NaOH(aq) Cu(OH)2(s)

 Alkalis react with some metals to produce a

- Zn(s) + 2NaOH(aq) Na2ZnO2(aq) +H2(g)

 A salt is formed when metallic or ammonium

 Acid salts – these are formed when some of the

 Basic salts – these are salts which contain oxide

- Eg. Iron(II) ammonium sulphate –

 Insoluble salts are prepared by ionic

 The elements which make up a compound are

 Basic – produces an alkaline solution mainly

 Amphoteric – reacts with both acids and alkalis

 Neutral – does not react with either acids or

You might also like