Question

explain the preparation of nitric acid by ostwald's process.

Answer 1

Question #57815, Chemistry / Inorganic Chemistry

Explain the preparation of nitric acid by Ostwald's process.

Answer:

Ostwald process consists from few stages through which nitric acid is produced from ammonia. As a first step, $\mathrm{NH}_3$ and oxygen catalytically react to form nitrogen monoxide NO:

$$4 \mathrm{NH}_3(\mathrm{g}) + 5 \mathrm{O}_2(\mathrm{g}) \rightarrow 4 \mathrm{NO}(\mathrm{g}) + 6 \mathrm{H}_2\mathrm{O}(\mathrm{g})$$

Industrial process occurs at $250^{\circ}\mathrm{C}$ under 5-10 atm pressure on a Pt-Rh catalyst.

In the next step, NO is further oxidized with oxygen to nitrogen dioxide $\mathrm{NO}_2$. No catalyst is required for this reaction, as it will occur even in air at room temperature:

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

On the last stage $\mathrm{NO}_2$ is absorbed with water to give nitric acid $(\mathrm{HNO}_3)$ and NO. The nitric acid is separated by distillation, and NO is again recycled to $\mathrm{NO}_2$.

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