What is the catalyst used for oxidation of $S O_{2}$ to $S O_{3}$ in lead chamber process for manufacture of sulphuric acid? (A) Nitric oxide (B) Nitrous oxide (C) Potassium iodide (D) Dilute $\mathrm{HCl}$

Correct option is A (Nitric oxide)
Explanation:
Nitric oxide (NO) is the catalyst used for oxidation of $\mathrm{SO}_{2}$ to $\mathrm{SO}_{3}$ in lead chamber process for manufacture of sulphuric acid. The overall reaction can be written as
$
2 \mathrm{SO}_{2}+\mathrm{O}_{2}+2 \mathrm{H}_{2} \mathrm{O} \stackrel{\mathrm{NO}}{\longrightarrow} 2 \mathrm{H}_{2} \mathrm{SO}_{4}
$