Question

Consider the following list of reagents:
Acidified $K _{2} Cr _{2} O _{7}$, alkaline $KMnO _{4}, CuSO _{4}, H _{2} O _{2}, Cl _{2}, O _{3}$ $FeCl _{3}, HNO _{3}$ and $Na _{2} S _{2} O _{3}$. The total number of reagents that can oxidise aqueous iodide to iodine is

• A. 4
• B. 5
• C. 6
• D. 7

Answer 1

Answer: (D)

$ 6 KI + K _{2} Cr _{2} O _{7}+7 H _{2} SO _{4} \rightarrow 4 K _{2} SO _{4}+ Cr _{2}\left( SO _{4}\right)_{3}$

$+3 I _{2}+7 H _{2} O$

$2 CuSO _{4}+4 KI \rightarrow Cu _{2} I _{2}+2 K _{2} SO _{4}+ I _{2}$

$H _{2} O _{2}+2 KI \rightarrow I _{2}+2 KOH$

$Cl _{2}+2 KI \rightarrow 2 KCl + I _{2}$

$O _{3}+2 KI + H _{2} O \rightarrow 2 KOH + I _{2}+ O _{2}$

$2 FeCl _{3}+2 KI \rightarrow 2 FeCl _{2}+2 KCl + I _{2}$

$4 HNO _{3}+2 KI \rightarrow 2 KNO _{3}+ NO _{2}+ I _{2}+2 H _{2} O$