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CHAPTER 8: SALTS

1. Classification andpreparation of salt

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Neutralisation using titration

Titration method

Evaporation/Heating

Cooling/crystallization

Filtration

Dry

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Salt Preparation

Salt type

(Na+, K+, NH4+)

Other than

(Na+, K+, NH4+)

Soluble salts Insoluble salts

Neutralisation Acid + Metal oxide

Acid + metallic carbonate

Acid + Metal

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Preparation of soluble salts other

than (Na+, K+, NH4+)

1. Acid + metal oxide Salt + water

Eg: HCl + MgO MgCl2 + H2O

2. Acid + metal Salt + hydrogen gas

Eg: 2HCl + Zn ZnCl2 + H2

3. Acid + metal carbonate Salt + water + carbon

dioxide

Eg: HCl + CuCO3 CuCl2 + H2O + CO2

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Metal/ metal oxide/

metal carbonate

Glass rod

Acid

Pour 50 cm3of sulphuric acid

into a beaker. Warm the acid.

Use a spatula to add copper(II)

oxide powder bit by bit into the

acid. Stir the mixture well.

Continue adding copper(II)oxide until some of it no longer

dissolves(excess unreactedmetal).

Step 1 -

Heating

See the change of metal solid

colour and dissolve

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Step 2 -

Filtration

Excess

unreacted

metal (residue)

Evaporating basinwith salt solution

(filtrate)

Solution salt contains

impurities.

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Step 3 Heating/Evaporation

Evaporatingbasin

Saltsolution

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Step 4 -

Cooling

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Step 5 -

Filtration

Step 6

Drying

Rinse

with

distilled

water

Glass

rod

Salt Cystals

The crystals are

filtered and rinsedwith a little cold

distilled water.

Filter

Paper

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Recrystallisation

Purpose: To purify impure salts because thesalts contain impurities

Steps:

1. Addingdistilledwater to

impure salt

2. Repeatheating/evaporation,

cooling, filtrationand drying process

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Regular geometricshapes such as cubicor hexagonal

Straight and sharpedges

Flat and smoothsurfaces

Surfaces that makedefinite angles withone another

Hard but brittle

Salt crystal characteristic

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Fastcrystallisation small crystals

Slow

crystallisation large crystals

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Now lets watch a

video aboutRecrystallisation

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Preparation of insoluble salts

Precipitation method

1. Mix two soluble salts aqueous solutions together

and react to form an insoluble salt and solublesalt.

Example:

Barium nitrate + sodium sulphate

Barium sulphate + sodium nitrate

2. This reaction is called double decomposition.

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Two aqueous solutions/soluble salts were

mixed together

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Mixture solutions

Filter paper

Retort

stand

Precipitate

(residue)

Filter

funnel

Aqueous

Solution

(filterate)

Glass

rod

Glass

rodDistilled

water

Precipitate

(residue)

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Filter paperPrecipitate

/Soluble

salts

Dried by pressing between two

pieces of filter paper.

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Do Activity 8.5

I l bl S l l i Ch i l E i I i

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Insoluble

Salt

Salt solution Chemical Equation Ionic

EquationCation Anion

Zinccarbonate,

ZnCO3

Zn(NO3 )2 Na2CO3 Zn(NO3 )2 + Na2CO3 ZnCO3 + 2NaNO3

Zn2+ + CO32- ZnCO3

Barium

sulphate,

BaSO4

Ba(NO3)2 K2SO4 Ba(NO3)2+K2SO4 BaSO4+ 2KNO3

Ba2+ + SO42-

BaSO4

Lead (II)

sulphate,PbSO4

Pb(NO3 )2 Na2SO4 Pb(NO3 )2 + Na2SO4

PbSO4 + 2NaNO3

Pb2+ + SO42-

PbSO4

Lead (II)

iodide,

PbI2

Pb(NO3 )2 KI Pb(NO3 )2 + 2KI

PbI2 + 2KNO3

Pb2+ + 2I-

PbI2

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Conclusion

Preparation ofsalts

Soluble Salts

Na+, K+, NH4+ -

Neutralisation

Other than Na+,K+, NH4

+

reaction withmetal, metal

oxide or metalcarbonate

Insoluble Salts Precipitationmethod