Question

In one of the following reactions $HNO _{3}$ does not behave as an oxidizing agent. Identify it:

• A. $I _{2}+10 HNO _{3} \rightarrow 2 HIO _{3}+10 NO _{2}+4 H _{2} O$
• B. $3 Cu +8 HNO _{3} \longrightarrow 3 Cu \left( NO _{3}\right)_{2}+2 NO +4 H _{2} O$
• C. $4 Z n+10 HNO _{3} \longrightarrow 4 Z n\left( NO _{3}\right)_{2}+ NH _{4} NO _{3}+3 H _{2} O$
• D. $2 HNO _{3}+ P _{2} O _{5} \longrightarrow 2 HPO _{3}+ N _{2} O _{5}$

Answer 1

Answer: (D)

[a] $I _{2}+10 \overset{+5}{HN} O _{3} \rightarrow 2 HIO _{3}+10 NO +4 H _{2} O$
In the reaction $ HNO _{3} $ is acting as oxidizing agent because to $+2 $.
[b] $3 Cu +8 \overset{+5}{HN } O _{3} \rightarrow 3 Cu \left( NO _{3}\right)_{2}+2 NO +4 H _{2} O$
It is reaction in which $HNO _{3}$ is acting as oxidising agent because oxidation number of nitrogen is decreasing.
[c] $4 Zn +10 \overset{+5}{HN} O _{3} \rightarrow 4 Zn \left( NO _{3}\right)_{2}$
$+ NH _{4} \overset{+2}{NO} _{3}+3 H _{2} O$
$\therefore $ It is also a reaction, in which $HNO _{3}$ is oxidizing agent.
[d] $2 HNO _{3}+ P _{2} O _{5} \rightarrow 2 HPO _{3}+ N _{2} O _{5}$
$P_{2} O_{5}$ dehydrating agent.
So in this reaction $HNO _{3}$ does not act as oxidizing agent.