Which of the following reactions do not involve oxidation reduction ?
I. `2Cs+2H_(2)Orarr2CsOH+H_(2)`
II. `2CuI_(2)rarr2CuI+I_(2)`
III. `NH_(4)Br+KOHrarrKBr+NH_(3)+H_(2)O`
IV. `4KCN+Fe(CN)_(2)rarrK_(4)[Fe(CN)_(6)]`

Options

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

Answer

D

Explanation

i. `{:(,RbrarrRb^(1)+e^(-)("Oxidation"),,,),(H_(2)O+,e^(-)rarroverset(ө)OH+(1)/(2)e^(-)("Oxidation"),,,):}]`
Hence, redox reaction.
ii. `{:(e^(-)+,Cu^(2+)rarrCu^(1+)("Reduction"),,,),(,2I^(ө)rarrI_(2)+2e^(-)("Reduction"),,,):}]`
Hence, redox reaction
iii. `underset(x=-3)overset(o+)(NH_(4))rarrunderset(x=-3)(NH_(3))`(No change in oxidation reaction).
Hence, reaction is not redox.
iv. No change in the oxidation number of either `Fe^(2+)` or `CN^(ө)` in both reactant and product, hence, not work reaction.