Question

HI cannot be prepared by the action of conc. $H_{2}S{O}_4$ on KI because $H_{2}S{O}_4$ is _____?

• A. oxidising agent
• B. reducing agent
• C. A and B
• D. None of these

Answer 1

The correct option is A oxidising agent

HI cannot be prepared by the action of conc. $H_{2}S{O}_4$ on KI because $H_{2}S{O}_4$ is an oxidising agent and HI is strong reducing agent.

HI reduces sulphuric acid to sulphur dioxide and itself is oxidised to iodine.

$KI+H_{2}S{O}_4\to KHS{O}_4+HI{H}_{2}S{O}_4+2HI\to S{O}_2+I_2+2H_{2}O$

Hence, HI is prepared by heating KI with conc. phosphoric acid. Same is true for the preparation of HBr.