Question

The preparation of lead sulphate from lead carbonate is a two-step process (lead sulphate cannot be prepared by adding dilute sulphuric acid to lead carbonate.)
(i) What is the first step that is required to prepare lead sulphate from lead carbonate?
(ii) Write the equation for the reaction that will take place when this first step is carried out.
(iii) Why is the direct addition of dilute sulphuric acid to lead carbonate an impractical method of preparing lead sulphate?

Answer 1

(i) The first step involves preparation of lead nitrate by reacting insoluble lead carbonate with dilute nitric acid.

(ii) The equation for the reaction that takes place in the first step is as follows:

$$\begin{gathered} {\mathrm{PbCO}}_3+2{\mathrm{HNO}}_3\to \mathrm{Pb}({\mathrm{NO}}_3{)}_2+{\mathrm{H}}_2\mathrm{O}+{\mathrm{CO}}_2 \\ \mathrm{Lead}\mathrm{carbonate}\mathrm{Lead}\mathrm{nitrate}(\mathrm{Soluble}) \end{gathered}$$

(iii) When dilute sulphuric acid is added to lead carbonate, insoluble lead sulphate covers the surface of insoluble lead carbonate and prevents it from further reaction with sulphuric acid. Thus, the reaction remains incomplete. So, the preparation of lead sulphate from lead carbonate involves two steps wherein insoluble lead carbonate is first converted to soluble lead nitrate and then reacted with sulphuric acid to produce lead sulphate.