Question

Zn gives $H_2$ gas with $H_2SO_4$ and HCI but not with $HNO_3$ because :-

• A. $Zn$ act as oxidising agent when react with $ HNO_3$
• B. $HBO_3$ is weaker acid than $H_2SO_4$ & HCI
• C. In electrochemical series Zn is placed above hydrogen
• D. $NO^{?}_{3}$ is reduced in preference to hydronium ion

Answer 1

The Correct Option is D

The correct option is(A): \(NO^{?}_{3}\) is reduced in preference to hydronium ion.

Zn have lower value of \(E_{cell}^*\) and easily gives 
oxidation. Zn is present above \(H_2\) in 
electrochemical series. So, it liberates hydrogen gas 
from dilu. \(HCI/H_2SO_4\). But \(HNO_3\) is an oxidising 
agent. The hydrogen obtained in this reaction is 
converted into \(H_2O.\) In \(HNO_3, \, NO_3^-\) ion is reduced 
and give \(NH_4 \, NO_3, \, N_2O, \, NO \, and \, NO_2\) (based upon 
the concentration of \(HNO_3\) ) 
[ \(Zn + 2HNO_3 \longrightarrow Zn \, ( NO_3)_2 + 2 H] \times 4\) 
(Nearly 6% ) 
\(HNO_3 + BH \longrightarrow NH_3 + 3H_2O\)
\(\frac{ NH_3 + HNO_2 \longrightarrow NH_4 \, NO_3}{ 4Zn + 10HNO_3 \longrightarrow 4 Zn ( NO_3)_2 + NH_4 \, NO_3 + 3H_2O}\)