Question

In the preparation of nitric acid from KNO₃ concentrated sulphuric acid is used in place of concentrated hydrochloric acid. Why?

Answer 1

• As hydrochloric acid is volatile and hence nitric acid vapours will carry hydrochloric vapours.
• Therefore concentrated hydrochloric acid cannot replace concentrated sulphuric acid for the preparation of Nitric acid.
• $\underset{\mathrm{potassium}\mathrm{nitrate}}{\underset{}{{\mathrm{KNO}}_3}}+\underset{\mathrm{sulphuric}\mathrm{acid}}{\underset{}{{\mathrm{H}}_2{\mathrm{SO}}_4}}\to \underset{\mathrm{potassium}\mathrm{hydrogen}\mathrm{sulphate}}{\underset{}{{\mathrm{KHSO}}_4}}+\underset{\mathrm{nitric}\mathrm{acid}}{\underset{}{{\mathrm{HNO}}_3}}$