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.)

1. What is the first step that is required to prepare lead sulphate from lead carbonate?
2. Write the equation for the reaction that will take place when this first step is carried out.
3. Why is the direct addition of dilute sulphuric acid to lead carbonate an impractical method of preparing lead sulphate?

Answer 1

1. The first step is to convert insoluble lead carbonate into soluble lead nitrate by treating lead carbonate with dilute nitric acid.
2. \[\ce{PbCO3_{(s)} + 2HNO3_{(dil)} -> Pb(NO3)2_{(aq)} + H2O_{(l)} + CO2}\]
3. Adding dilute sulphuric acid (H₂SO₄) to lead carbonate (PbCO₃) to prepare lead sulphate (PbSO₄) is impractical because an insoluble crust of lead sulphate forms on the lead carbonate, preventing further reaction.