Question

Which of the following represents a disproportionation reaction?

• A. $N_{2(g)}+O_{2(g)}\to 2N{O}_{(g)}$
• B. $pb{\left(N{O}_3\right)}_{2\left(s\right)}\to pb{O}_{\left(s\right)}+2N{O}_{2\left(g\right)}+1/2O_{2\left(g\right)}$
• C. $Na{H}_{\left(s\right)}+H_2{O}_{\left(l\right)}\to NaO{H}_{\left(aq\right)}+H_2\left(g\right)$
• D. $2N{O}_{2\left(g\right)}+2O{H}_{\left(aq\right)}^{-}\to N{O}_{2\left(aq\right)}^{-}+N{O}_{3\left(aq\right)}^{-}+H_2{O}_{\left(l\right)}$

Answer 1

Answer: (D)

(a) ${\stackrel{0}{N}}_{2(g)}+{\stackrel{0}{O}}_{2(g)}\to 2\stackrel{+2}{N}\stackrel{-2}{O_{(g)}}$
It is a combination (combustion) type of redox reaction
(b) $2\stackrel{+2}{\mathrm{pb}}\stackrel{+5-2}{(N{O}_3{)}_{2(s)}}\to 2\stackrel{+2}{\mathrm{pb}}\stackrel{-2}{O_{(s)}}+2\stackrel{+4}{N}\stackrel{-2}{O_{2(g)}}+\frac{1}{2}{\stackrel{0}{O}}_{2(g)}$
It is also a redox reaction involving decomposition of lead nitrate
(c) $\stackrel{+1}{\mathrm{Na}}\stackrel{-1}{H_{(s)}}+\stackrel{+1}{H_2}\stackrel{-2}{O_{(l)}}\to \stackrel{+1}{\mathrm{Na}}\stackrel{-2}{O}\stackrel{+1}{H_{(aq)}}+{\stackrel{0}{H}}_{2(g)}$
It is a displacement type of redox reaction in which hydrogen of water is displaced by a hydride ion into dihydrogen gas
(d) $2\stackrel{+4}{N}\stackrel{-2}{O_2}+2\stackrel{-2}{O}\stackrel{+1}{H}\to \stackrel{+3}{N}\stackrel{-2}{O_{2(aq)}^{-}}+\stackrel{+5}{N}\stackrel{-2}{O_{3(aq)}^{-}}+H_2{O}_{(l)}$
It is a disproportionation reaction in which the oxidation state of nitrogen changes from $+4$ to $+3$ and $+5$