Question

Presence of which reagent will affect the reversibility of the following reaction, and change it to a irreversible reaction.
$C{H}_4+I_2\underset{\text{Reversible}}{\stackrel{hv}{\rightleftharpoons }}C{H}_3-I+HI$

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• A. Liquid $N{H}_3$
• B. Concentrated $HI{O}_3$
• C. HOCI
• D. Dilute $HN{O}_2$

Answer 1

The correct option is B Concentrated $HI{O}_3$

Iodination is very slow and a reversible reaction.
Formed $HI$ in product side is powerful reducing agent, it will reduced alklyl iodide to $I_2$.
The reaction can be irreversible in the presence of strong oxidising agent like $conc.HN{O}_{3}orconc.HI{O}_3.$ It will oxidise the $HI$ to $I_2$ and make the reaction irreversible.

$C{H}_4+I_2\rightleftharpoons C{H}_3-I+HI$

$HI{O}_3+5HI\to 3I_2+3H_{2}O$