Question

In which of the following reactions, the underlined substance has been oxidized?

• A. $\underline{Br_2} + \underline{H_2S} \rightarrow 2 HBr + S$
• B. $\underline{2HgCl_2 } + SnCl_2 \rightarrow \underline{Hg_2Cl_2} + SnCl_4$
• C. $Cl_2 + 2 \underline{KI} \rightarrow 2KCl + \underline{I_2}$
• D. $\underline{2Cu^{2+} } + 4 I^{-}\rightarrow \underline{Cu_2I_2} + I_2 $

Answer 1

Answer: (C)

(a) $\overset{\text{ 0}}{Br_2 } \rightarrow \overset{\text{-1}}{HBr } $
(b) $\overset{\text{ +2}}{HgCl_2} \rightarrow \overset{\text{ +1 }}{Hg_2} Cl_2$
(c) $2 \overset{\text{-1}}{KI} \rightarrow \overset{\text{0}}{I_2}$
(d) $2 \, Cu^{2+} \rightarrow \overset{\text{+1}}{Cu_2} I_2$
Only in (c) the O.N. of I increases from - 1 to 0 and hence KI gets oxidised to $I_2$.