Question

Oleum is formed by combining sulphuric acid with:

• A. sulphur dioxide
• B. sodium sulphide
• C. sulphur trioxide
• D. sulphur

Answer 1

The correct option is C sulphur trioxide

Oleum is a solution of sulfur trioxide in sulfuric acid.It has a general formula of $H_{2}S{O}_4.nS{O}_3$, i.e., “n” moles of trioxide per 1 mol of acid.

$H_{2}S{O}_4+nSO3\to H_{2}S{O}_4.nS{O}_3$ or $H_2{S}_2{O}_7$

So the Oleum is formed by combining sulphuric acid with srectulfur trioxide.

Hence option C is correct.