Question

Give the equation for the preparation of each of the following salts from the starting material given.
(i) Copper sulphate from copper (II) oxide,
(ii) Iron (III) chloride from Iron.
(iii) Potassium sulphate from potassium hydroxide solution.
(iv) Lead chloride from lead carbonate (two equations).

Answer 1

(i) Copper sulphate is prepared by the neutralisation reaction of insoluble copper oxide with dilute sulphuric acid.

$\mathrm{CuO}+{\mathrm{H}}_2{\mathrm{SO}}_4\to {\mathrm{CuSO}}_4+{\mathrm{H}}_2\mathrm{O}$

(ii) When dried chlorine gas is passed over heated iron, it forms anhydrous iron (III) chloride.

$$\begin{gathered} 2\mathrm{Fe}+3{\mathrm{Cl}}_2\to 2{\mathrm{FeCl}}_3 \\ \mathrm{Anhydrous} \\ \mathrm{iron}\left(\mathrm{III}\right)\mathrm{chloride} \end{gathered}$$

(iii) Potassium sulphate is formed when potassium hydroxide solution is treated with sulphuric acid.

$$\begin{gathered} 2\mathrm{KOH}+{\mathrm{H}}_2{\mathrm{SO}}_4\to {\mathrm{K}}_2{\mathrm{SO}}_4+2{\mathrm{H}}_2\mathrm{O} \\ \mathrm{Potassium} \\ \mathrm{sulphate} \end{gathered}$$

(iv) Preparation of lead chloride from lead carbonate involves the following steps:
Step I: Insoluble lead carbonate first reacts with dilute nitric acid to form soluble lead nitrate.

${\mathrm{PbCO}}_3+2{\mathrm{HNO}}_3\to \mathrm{Pb}({\mathrm{NO}}_3{)}_2+{\mathrm{H}}_2\mathrm{O}+{\mathrm{CO}}_2$

​ Step II: Dilute hydrochloric acid is then added to lead nitrate to form lead chloride.

$\mathrm{Pb}({\mathrm{NO}}_3{)}_2+2\mathrm{HCl}\to {\mathrm{PbCl}}_2+2{\mathrm{HNO}}_3$