ACID, BASE AND SALT

CHAPTER 6 : ACID, BASE AND SALT

6.1 : THE ROLE OF WATER IN SHOWING ACIDIC AND ALKALINE PROPERTIES

.ACID

. .examples
of acids

BASICITY OF . .
ACIDS .
.monoprotic .

Basicity of .
acids

.BASE

. .examples
of base

Base that dissolve in water is known as alkali. .
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ALKALI

.

Examples
of alkali
..

.

.
uses of
acids and
alkali

..

with water acid/alkali will ionise produce H+/OH-

without water . .

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6.2 : pH VALUE

pH value is pOH = - log [OH+] pH + pOH = 14
pH = - log [H+] pH = 14 - pOH

The higher the pH value

the lower the pH value

6.3 : STRENGTH OF ACIDS AND ALKALIS

weak acid . .

Example : CH3COOH ⇔ CH3COO- + H+ . .

strong acid

Example : ______________________________________________________

weak alkali . .

Example : ____________________________________________________

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strong alkali . .

Example : ____________________________________________________

6.4 : CHEMICAL PROPERTIES OF ACIDS AND ALKALIS

1. Chemical properties of acids:

2. Chemical properties of alkalis:
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6.5 : CONCENTRATION OF AQUEOUS SOLUTION

Number of moles, n = MV

6.6 STANDARD SOLUTION

M1V1 = M2V2

Preparation of standard solution by diluting aqueous solution

During dilution, water that is added to the aqueous solution will alter the concentration of

the solution but it would not alter the number of moles of solute contained in the solution.
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6.7 : NEUTRALISATION

Acid + Alkali → Salt + Water

Aplications of .
neutralisation in daily life

Ionic equation for neutralisation reaction

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Titration method

End point is
Perubahan warna penunjuk takat akhir peneutralan :

No Indicator Acidic Colour in medium Alkaline
Neutral
1 Phenolphthalein
2 Methyl orange

Solving numerical problems involving neutralisation

MaVa = a
MbVb b

6.8. SALTS, CRYSTALS AND THEIR USES IN DAILY LIFE

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Physical properties of salt crystals .

.
.

. .

Examples of salts and their uses •.
.
•. .

. •.

.
•.

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6.9 PREPARATION OF SALTS

Solubility of salts in water

Type of salts Soluble in water Insoluble in water

Preparation of soluble salts

Construction of ionic equations through the continuous variation method
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6.11 ACTION OF HEAT ON SALTS

When salt is heated, it will produce a gas

Gas tests
-How to test the gas produced?

Gas Method Observation Inference
Carbon dioxide Carbonate salt
Sulphate salt
Sulphur dioxide
Nitrate salt
Nitrogen dioxide Nitrate salt
Chloride salt
Oxygen gas Ammonium salt

Chlorine gas

Ammonia gas

hydrogen chloride
gas

Hydrogen gas

Effect of heat
-Most salts decompose when heated.

Colour of the salt Salt The gas released
and te residue is heat gas is used to identify
used to identify
anion
cation

Salt Equation
CO2-3

NO-3

SO2-4

Cl- NH4Cl

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Colour of residue Metal oxide Cation present in
Colour of residue the salt
Copper(II)oxide
Hot Cold Zinc oxide

Black Black Lead(II) oxide
Yellow White
Brown yellow

6.11 QUALITATIVE ANALYSIS OF SALTS

Qualitative analysis to identify cations and anions in salts

....

A.Observations on physical properties of salts

-All white soluble salts dissolve in water to form colourless slat solutions.

Salts Colour

Solid state Aqueous solution

Green Green

Brown Brown

Blue Blue

Green Insoluble in water

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B. Effect of heat on salts and gas tests

Colour of residue Inference Gas produced Inference

Hot Cold Copper(II) ion Carbonate salt
Zinc ion Nitrate salt
Black Black Ammonium
Yellow White Lead(II) ion salt
Brown yellow Iron(II) ion Might be
nitrate salt or
Ag2CO3

C.Anion test

Anion

Carbonate Chloride Sulphate Nitrate
ion ion ion ion

dilute Dilute AgNO3 Dilute Brown
HCl HNO3 HCl ring

White White
precipitate precipitate

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D.Cation test

Add NaOH solution

Cation

Precipitate No
precipitate
Coloured Dissolve in excess NaOH White Not dissolve in
excess NaOH .

Cu2+ Fe2+ Fe3+ Pb2+ Zn2+ Al3+ Mg2+ Ca2+ NH4+

Add NH3 solution Cation

Precipitate No
precipitate

Coloured Dissolve in excess NH3 White Not dissolve in .
excess NH3

Cu2+ Fe2+ Fe3+ Zn2+ Mg2+ Al3+ Pb2+ NH4+

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E.Confirmatory tests for cations

Ions Confirmatory test Observation
Fe 2+ Add potassium hexacyanoferrate (III) Dark blue precipitate is formed
K3Fe(CN)6 solution
Fe 3+
Add potassium thiocyanate, KSCN Blood red solution is formed

A few drops of potassium Dark blue precipitate is formed

hexacyanoferrate (II) K4Fe(CN)6 solution

Pb 2+ Add potassium iodide solution, KI and Yellow precipitate dissolves
heated when heated and reappears
when cooled

NH + Add Nessler reagent Brown precipitate is formed

4

Add dilute sodium hydroxide, NaOH Colourless gas turns moist red
solution and heat litmus paper blue

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