Question
On addition of cone. $${H_2}S{O_4}$$ to a chloride salt, colourless fumes are evolved but in case of iodide salt, violet fumes come out. This is because
A.
$${H_2}S{O_4}$$ reduces $$HI$$ to $${I_2}$$
B.
$$HI$$ is of violet colour
C.
$$HI$$ gets oxidised to $${I_2}$$
D.
$$HI$$ changes to $$HI{O_3}.$$
Answer :
$$HI$$ gets oxidised to $${I_2}$$
Solution :
$$HI$$ being a stronger reducing agent than $${H_2}S{O_4},$$ reduces $${H_2}S{O_4}$$ to $$S{O_2}$$ and is itself oxidised to $${I_2}$$ ( violet fumes ).
$$\eqalign{
& MI + {H_2}S{O_4} \to MHS{O_4} + HI \cr
& {H_2}S{O_4} \to {H_2}O + S{O_2} + \left[ O \right] \cr
& 2HI + \left[ O \right] \to {H_2}O + \mathop {{I_2}}\limits_{{\text{(violet fumes)}}} \cr} $$