CAIE IGCSE Chemistry 7.3.4 Preparation of insoluble salts by

Practise preparing insoluble salts by precipitation, choosing aqueous reactants and separating a clean dry solid from the mixture.

Exam points

choose two soluble aqueous salts that supply ions for the required precipitate
describe filtering, washing and drying the residue to obtain a pure insoluble salt
distinguish precipitation from crystallisation, titration and excess-solid methods

[Maximum number: 1]

Some symbol equations and word equations, A to J, are shown.

$A $\mathrm{Fe}^{3+}+3 \mathrm{OH}^{-} \rightarrow \mathrm{Fe}(\mathrm{OH})_{3}$$

$B $\mathrm{H}^{+}+\mathrm{OH}^{-} \rightarrow \mathrm{H}_{2} \mathrm{O}$$

C ethane + chlorine → chloroethane + hydrogen chloride

$D $\mathrm{C}_{12} \mathrm{H}_{26} \rightarrow \mathrm{C}_{8} \mathrm{H}_{18}+\mathrm{C}_{4} \mathrm{H}_{8}$$

E ethene + steam → ethanol
F chlorine + aqueous potassium iodide → iodine + aqueous potassium chloride

$G $\mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6} \rightarrow 2 \mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH}+2 \mathrm{CO}_{2}$$

H ethanoic acid + ethanol → ethyl ethanoate + water
I calcium carbonate → calcium oxide + carbon dioxide

$J $6 \mathrm{CO}_{2}+6 \mathrm{H}_{2} \mathrm{O} \rightarrow \mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6}+6 \mathrm{O}_{2}$$

Use the equations to answer the questions that follow.
Each equation may be used once, more than once, or not at all.
Give the letter, A to J, for the equation that represents:

a precipitation reaction [1]

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7.3.4—Preparation of insoluble salts by question 1