Chemistry - Complete P-block Question with Solution | TestHub

The Ostwald process is an industrial method for producing nitric acid (HNO₃). It involves three main steps:

1. Catalytic oxidation of ammonia:

$$4{\mathrm{NH}}_3(\mathrm{g})+5{\mathrm{O}}_2(\mathrm{g})\underset{500K,9bar}{\overset{Pt/Rh-gaugecatalyst}{\to }}4\mathrm{NO}(\mathrm{g})+6{\mathrm{H}}_2\mathrm{O}(\mathrm{g})$$

This reaction is represented by option A.

2. Oxidation of nitric oxide:

$$2\mathrm{NO}(\mathrm{g})+{\mathrm{O}}_2(\mathrm{g})\rightleftharpoons 2{\mathrm{NO}}_2(\mathrm{g})$$

This reaction is represented by option B.

3. Absorption of nitrogen dioxide in water:

$$3{\mathrm{NO}}_2(\mathrm{g})+{\mathrm{H}}_2\mathrm{O}(\ell )\to 2{\mathrm{HNO}}_3(\mathrm{aq})+\mathrm{NO}(\mathrm{g})$$

This reaction is represented by option C. The NO produced is recycled.

Option D describes the preparation of nitric acid from nitrates and sulfuric acid, which is a laboratory method, not part of the industrial Ostwald process.

Therefore, the reaction not involved in the Ostwald process is D.