• # question_answer $HI$ cannot be prepared by the action of conc. ${{H}_{2}}S{{O}_{4}}$ on $KI$ because [MNR 1984] A) $HI$ is stronger than ${{H}_{2}}S{{O}_{4}}$ B) $HI$ is more volatile than ${{H}_{2}}S{{O}_{4}}$ C) ${{H}_{2}}S{{O}_{4}}$ is an oxidising agent D) ${{H}_{2}}S{{O}_{4}}$ forms complex

$KI+{{H}_{2}}S{{O}_{4}}\,\to \,KHS{{O}_{4}}+HI$ HI is formed but it is further oxidised by conc. ${{H}_{2}}S{{O}_{4}}$ into ${{I}_{2}}$ $2HI+{{H}_{2}}S{{O}_{4}}\,\to \,2{{H}_{2}}O+\underset{\text{Violet vapour}}{\mathop{{{I}_{2}}+S{{O}_{2}}}}\,\uparrow$