Question

Oleum is a mixture of sulphuric acid and .

• A. sulphur trioxide
• B. water
• C. sulphurous acid

Answer 1

The correct option is A sulphur trioxide

Oleum $\left(H_2{S}_2{O}_7\right)$, also known as pyrosulphuric acid, is a mixture of sulphuric acid $\left(H_{2}S{O}_4\right)$ and sulphur trioxide $\left(S{O}_3\right)$.

In contact process, sulphur trioxide is absorbed in concentrated sulphuric acid to form oleum. Further, oleum is diluted to produce sulphuric acid.

$H_2{\mathrm{SO}}_4\left(\mathrm{aq}\right)+{\mathrm{SO}}_3\left(g\right)\to H_2{S}_2{O}_7\left(\mathrm{aq}\right)$