Question

Which of the following reactions do not involve oxidation-reduction?
I. $2Cs+2H_{2}O⟶2CsOH+H_2$
II. $2Cu{I}_2⟶2CuI+I_2$
III. $N{H}_{4}Br+KOH⟶KBr+N{H}_3+H_{2}O$
IV. $4KCN+Fe{\left(CN\right)}_2⟶K_4\left[Fe{\left(CN\right)}_6\right]$

• A. I, II
• B. I, III
• C. I, III, IV
• D. III, IV

Answer 1

The correct option is D III, IV

i. $Cs⟶{Cs}^{1+}+e^{-}$ (Oxidation)
$H_{2}O+e^{-}⟶\stackrel{\ominus }{O}H+\frac{1}{2}{H}_2$ (Reduction)
Hence, it is a redox reaction.
ii. $e^{-}+{Cu}^{2+}⟶{Cu}^{1+}$ (Reduction)
$2I^{\ominus }⟶I_2+2e^{-}$ (Oxidation)
Hence, it is a redox reaction.
iii. No change in oxidation number.
Hence, the above reaction is not redox.
iv. No change in the oxidation number of either ${Fe}^{2+}$ or ${CN}^{\ominus }$ in both reactant and product occurs.
Hence, it is not a redox reaction.