JEE Main On 08 April 2018 Question 8
Question: Hydrogen peroxide oxidises $ {{[Fe{{(CN)}_6}]}^{4-}} $ to $ {{[Fe{{(CN)}_6}]}^{3-}} $ in acidic medium but reduces $ {{[Fe{{(CN)}_6}]}^{3-}} $ to $ {{[Fe{{(CN)}_6}]}^{4-}} $ in alkaline medium. The other products formed are, respectively: [JEE Main Online 08-04-2018]
Options:
A) $ {H_2}O $ and $ \text{(}{H_2}O+O _2) $
B) $ {H_2}O $ and $ \text{(}{H_2}\text{O+O}{H^{-}}\text{)} $
C) $ \text{(}{H_2}\text{O+}{O_2}\text{)} $ and $ {H_2}O $
D) $ \text{(}{H_2}\text{O+}{O_2}\text{)} $ and $ \text{(}{H_2}\text{O+O}{H^{-}}\text{)} $
Show Answer
Answer:
Correct Answer: A
Solution:
Reaction in acidic medium: $ {H_2}{O_2}\text{+2}{H^{+}}\text{+2}{e^{–}}\xrightarrow{{}}2{H_2}O $
$ {H_2}{O_2} $ oxidises $ {{[\text{ Fe(CN}{{)}_6}]}^{4-}}\text{ to }[\text{ Fe(CN}{{)}_6}{{]}^{\text{3–}}} $
and get reduced to $ {H_2}O $ . Reaction in basic medium: $ {H_2}O _2+2O{H^{-}}\xrightarrow{{}}O _2+2H _2O+2{e^{-}} $
$ H _2O _2 $ reduces $ {{[ Fe{{( CN )}_6} ]}^{\text{3–}}} $ to $ {{[ Fe{{( CN )}_6} ]}^{\text{4–}}} $
in alkaline medium and oxidised itself to $ O _2 $
