Q59 / 200 · NEET 2002 · Chemistry

$\mathrm{Zn}$ gives $\mathrm{H}_2$ gas with $\mathrm{H}_2 \mathrm{SO}_4$ and $\mathrm{HCl}$ but not with $\mathrm{HNO}_3$ because:

  • A
    $\mathrm{Zn}$ acts as an oxidizing agent when reacts with $\mathrm{HNO}_3$
  • B
    $\mathrm{HNO}_3$ is weaker acid than $\mathrm{H}_2 \mathrm{SO}_4$ and $\mathrm{HCl}$
  • C
    in electrochemical series $\mathrm{Zn}$ is above hydrogen
  • Correct answer
    D
    $\mathrm{NO}_3^{-}$is reduced in preference to hydronium ion

Solution

Nitric acid $\left(\mathrm{HNO}_3\right)$ is a strong oxidising agent. The Hydrogen gas produced during its reaction with metal gets oxidised to $\mathrm{H}_2 \mathrm{O}$, hence no hydrogen gas is produced. Usually when $\mathrm{Zn}$ reacts with acid, it acts as a reducing agent which gets oxidised to a salt and the acid is the oxidising agent which gets reduced to hydrogen gas.

Hence, the correct answer is option: 'D'.

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