CAIE IGCSE Chemistry Salt Preparation Question Bank

Practise selecting a salt-preparation route from solubility and reactant type, then applying titration, excess solid, crystallisation or precipitation steps.

Exam points

choose titration for a soluble salt made from an acid and alkali, then repeat without indicator
use excess metal, base or carbonate for a soluble salt and filter before crystallising
prepare an insoluble salt by precipitation, then filter, wash and dry the solid

Covered syllabus points

7.3.1—Preparation, separation and 7.3.2—Salt solubility rules: soluble 7.3.3—Hydrated substance as a substance that 7.3.4—Preparation of insoluble salts by 7.3.5—Term water of crystallisation as the

[Maximum number: 5]

Sulfur is an important element.

(a)

Dilute sulfuric acid is used to make salts known as sulfates.

A method consisting of three steps is used to make zinc sulfate from zinc carbonate.
step 1 Add an excess of zinc carbonate to $20 \mathrm{~cm}^{3}$ of $0.4 \mathrm{~mol} / \mathrm{dm}^{3}$ dilute sulfuric acid until the reaction is complete.
step 2 Filter the mixture.
step 3 Heat the filtrate until a saturated solution forms and then allow it to crystallise.

[ 5 ]

(i)

State two observations which would show that the reaction is complete in step 1.

1

2

[ 2 ]

M1 No more fizzing;

M2 $\left(\mathrm{ZnCO}_{3}\right)$ stops dissolving or a (white) solid remains / is visible

(ii)

Why is it important to add an excess of zinc carbonate in step 1?

[ 1 ]

To use up all the acid / $\mathrm{H}^{+}$ ions

(iii)

Name another zinc compound which could be used to make zinc sulfate from dilute sulfuric acid using this method.

[ 1 ]

(iv)

Suggest why this method would not work to make barium sulfate from barium carbonate and dilute sulfuric acid.

[ 1 ]

[Maximum number: 1]

A student prepares calcium nitrate, $\mathrm{Ca}\left(\mathrm{NO}_{3}\right)_{2}$ , by adding calcium carbonate to dilute nitric acid.

Calcium nitrate crystals are hydrated and have the formula $\mathrm{Ca}\left(\mathrm{NO}_{3}\right)_{2} \cdot x \mathrm{H}_{2} \mathrm{O}$ where x is a whole number of molecules of water.

The student heats the crystals to remove the molecules of water.

\mathrm{Ca}\left(\mathrm{NO}_{3}\right)_{2} \cdot x \mathrm{H}_{2} \mathrm{O}(\mathrm{~s}) \rightarrow \mathrm{Ca}\left(\mathrm{NO}_{3}\right)_{2}(\mathrm{~s})+x \mathrm{H}_{2} \mathrm{O}(\mathrm{~g})

State the term used to describe the calcium nitrate after the molecules of water have been removed.

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Covered syllabus points

7.3 Preparation of salts question 1

Question (a)

Question (i)

Question (ii)

Question (iii)

Question (iv)

7.3 Preparation of salts question 2