Question

Given the sequence of reactions,
$$\begin{gathered} {\mathrm{NH}}_2{\mathrm{NO}}_{2\left(\mathrm{aq}\right)}+{\mathrm{OH}}_{\left(\mathrm{aq}\right)}^{-}\underset{}{\to }{\mathrm{NH}}_4{\mathrm{NO}}_{2\left(\mathrm{aq}\right)}^{-}+{\mathrm{H}}_2{\mathrm{O}}_{\left(l\right)} \\ {\mathrm{NH}}_4{\mathrm{NO}}_{2\left(\mathrm{aq}\right)}^{-}\underset{}{\to }{\mathrm{N}}_2{\mathrm{O}}_{\left(\mathrm{g}\right)}+{\mathrm{OH}}_{\left(\mathrm{aq}\right)}^{-} \end{gathered}$$
The catalyst for the overall reaction is,
(a) ${\mathrm{OH}}_{\left(\mathrm{aq}\right)}^{-}$
(b) NH₂NO_{2 (aq)}
(c) ${\mathrm{NH}}_4{\mathrm{NO}}_2^{-}{}_{\left(\mathrm{aq}\right)}$
(d) N₂O_(g)

Answer 1

(a) ${\mathrm{OH}}_{\left(\mathrm{aq}\right)}^{-}$

The overall reaction can be represented as

${\mathrm{NH}}_2{\mathrm{NO}}_2\left(\mathrm{aq}.\right)\to {\mathrm{N}}_2\mathrm{O}\left(\mathrm{g}\right)+{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)$

A catalyst is a substance that speeds up the rate of a chemical reaction but is not consumed during the course of the reaction. A catalyst will appear in the steps of a reaction mechanism, but it will not appear in the overall chemical reaction.

On this basis, for the given sequence of reactions, the catalyst for the overall reaction is ${\mathrm{OH}}_{\left(\mathrm{aq}\right)}^{-}$.