Zn gives {H}₂ gas with {H}₂ {SO}₄ and {HCl} but not with {HNO}₃ because (2002)

$\mathrm{H}_{2} \mathrm{SO}_{4}$ act as oxidising agent when react with $\mathrm{HCl}$
$\mathrm{NO}_{3}^{-}$ is weaker acid than ${H}_{2} {SO}_{4}$ and $HCl$
In electrochemical series Zn is above hydrogen
${NO}_{3}^{-}$ is reduced in preference to hydronium ion.

Solution:

Zinc is on the top position of hydrogen in electrochemical series. So, Zn displaces

\mathrm{H}_{2}

from dilute

\mathrm{H}_{2} \mathrm{SO}_{4}

and

\mathrm{HCl}

with liberation of

\mathrm{H}_{2}

\mathrm{Zn}+\mathrm{H}_{2} \mathrm{SO}_{4} \rightarrow \mathrm{ZnSO}_{4}+\mathrm{H}_{2}

\mathrm{HNO}_{3}

On the other hand

\mathrm{H}_{2} \mathrm{O}

is an oxidising agent. Hydrogen obtained in this reaction is converted into

\mathrm{Zn}+4 \mathrm{HNO}_{3} \rightarrow \mathrm{Zn}(\mathrm{NO}_{3})_{2} +2 \mathrm{NO}_{2}+2 \mathrm{H}_{2} \mathrm{O}

\mathrm{Zn}

\mathrm{HNO}_{3}

\mathrm{HNO}_{3}

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