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. l, II
B. I,III
C. l,lll,IV
D. lll,IV

Answer

D

Explanation

(d) I. `Cs rarr Cs^(1+) + e^(-)` (Oxidation)
`H_2O + e^(-) rarr overline(O)H +1/2H_2`(Reduction)
Hence, redox reaction.
II. `e^(-) + Cu^(2+) rarr Cu^(1+)` (Reduction)
`2I^(-) rarr l_2 +2e^(-)` (Oxidation)
Hence, redox reaction.
II. `N overset(+)(H)_4 rarr NH_3` (No change in oxidation number)
Hence, reaction is not a redox reaction.
IV. No change in the oxidation number of either `Fe_(2+)` or `CN^(-)` in both reactant and product, hence, reaction is not a redox reaction.