Question

In one of the following reactions $HN{O}_3$ does not behave as an oxidizing agent. Identify it:

• A. $I_2+10HN{O}_3\to 2HI{O}_3+10N{O}_2+4H_{2}O$
• B. $3Cu+8HN{O}_3⟶3Cu{\left(N{O}_3\right)}_2+2NO+4H_{2}O$
• C. $4Zn+10HN{O}_3⟶4Zn{\left(N{O}_3\right)}_2+N{H}_{4}N{O}_3+3H_{2}O$
• D. $2HN{O}_3+P_2{O}_5⟶2HP{O}_3+N_2{O}_5$

Answer 1

Answer: (D)

[a] $I_2+10\stackrel{+5}{\mathrm{HN}}{O}_3\to 2HI{O}_3+10NO+4H_{2}O$
In the reaction $HN{O}_3$ is acting as oxidizing agent because to $+2$.
[b] $3Cu+8\stackrel{+5}{\mathrm{HN}}{O}_3\to 3Cu{\left(N{O}_3\right)}_2+2NO+4H_{2}O$
It is reaction in which $HN{O}_3$ is acting as oxidising agent because oxidation number of nitrogen is decreasing.
[c] $4Zn+10\stackrel{+5}{\mathrm{HN}}{O}_3\to 4Zn{\left(N{O}_3\right)}_2$
$+N{H}_4{\stackrel{+2}{\mathrm{NO}}}_3+3H_{2}O$
$\therefore$ It is also a reaction, in which $HN{O}_3$ is oxidizing agent.
[d] $2HN{O}_3+P_2{O}_5\to 2HP{O}_3+N_2{O}_5$
$P_2{O}_5$ dehydrating agent.
So in this reaction $HN{O}_3$ does not act as oxidizing agent.