Question

With reference to the redox properties of hydrogen peroxide $\left( H _{2} O _{2}\right)$. which of these reactions are feasible?
(i) $2 Fe ^{2+}+2 H ^{+}+ H _{2} O _{2} \rightarrow 2 Fe ^{3+}+2 H _{2} O$
(ii) $2 MnO _{4}^{-}+6 H ^{+}+5 H _{2} O _{2} \rightarrow 2 Mn 62++8 H _{2} O +5 O _{2}$
(iii) $2 Fe ^{2+}+ H _{2} O _{2} \rightarrow 2 Fe ^{3+}+2 OH ^{-}$
(iv) $2 MnO _{4}^{-}+3 H _{2} O _{2} \rightarrow 2 MnO _{2}+2 H _{2} O +3 O _{2}+2 OH ^{-}$

• A. (i) and (ii) only
• B. (ii) and (iv) only
• C. (i), (ii), (iii) and (iv)
• D. (ii), (iii) and (iv) only

Answer 1

Answer: (C)

$\because H _{2} O _{2}$ show oxidising as well as reducing action.
Oxidising nature (i.e. act as oxidising agent)
(i) In acidic solution,
$H _{2} O _{2}+2 H ^{+}+2 e^{-} \rightarrow 2 H _{2} O$
(ii) In alkaline solution,
$H _{2} O _{2}+2 e^{-} \rightarrow 2 OH ^{-}$
Reducing nature (i.e. act as reducing agent)
$\underset{\text { (n acidic medium) }}{ H _{2} O _{2}} \longrightarrow 2 H ^{+}+ O _{2}+2 e^{-}$
$\underset{\text{(in alkaline medium)}}{H _{2} O _{2}+2 OH ^{-}} \longrightarrow 2 H _{2} O + O _{2}+2 e^{-}$