Question

$Zn$ gives $H_2$ gas with $H_{2}S{O}_4$ and $HCl$ but not with $HN{O}_3$

• A. $Zn$ act as oxidising agent when react with $HN{O}_3$
• B. $HN{O}_3$ is weaker acid than $H_{2}S{O}_4$ and $HCl$
• C. In electrochemical series $Zn$ is above hydrogen
• D. ${NO}_3^{-}$ is reduced in preference to hydronium ion

Answer 1

Answer: (D)

${NO}_3^{-}$ is reduced in preference to hydronium ion

$Zn$ is present above $H_2$ in electrochemical series. So, it liberates hydrogen gas from dilute $HCl/H_{2}S{O}_4$. But $HN{O}_3$ is a strong oxidising agent so it oxidises the hydrogen obtained into $H_{2}O$.

In $HN{O}_3$, ${NO}_3^{-}$ ion is reduced and give $N{H}_{4}N{O}_3$, $N_{2}O$, $NO$ and $N{O}_2$ (based upon the concentration of $HN{O}_3$).

$4Zn+10HN{O}_3⟶4Zn{\left(N{O}_3\right)}_2+N{H}_{4}N{O}_3+3H_{2}O$