When sodium chloride reacts with sulfuric acid, a gas is evolved which gives dense white fumes with ammonia. Which gas is evolved?

The correct option is A

$\mathrm{HCl}$

The explanation for the correct option (A):

• When Sodium chloride ($\mathrm{NaCl}$) is added to Sulfuric acid (${\mathrm{H}}_2{\mathrm{SO}}_4$), Sodium hydrogen sulfate (${\mathrm{NaHSO}}_4$) is formed along with the liberation of Hydrogen chloride gas ($\mathrm{HCl}$).
• The reaction between $\mathrm{NaCl}$ and ${\mathrm{H}}_2{\mathrm{SO}}_4$ is:

$\mathrm{NaCl}\left(\mathrm{s}\right)+{\mathrm{H}}_2{\mathrm{SO}}_4\left(\mathrm{aq}\right)\to {\mathrm{NaHSO}}_4\left(\mathrm{aq}\right)+\mathrm{HCl}\left(\mathrm{g}\right)$

• The $\mathrm{HCl}$ gas, thus evolved reacts with Ammonia gas (${\mathrm{NH}}_3$) to produce dense white fumes of Ammonium chloride gas (${\mathrm{NH}}_4\mathrm{Cl}$).
• The reaction between $\mathrm{HCl}$ and ${\mathrm{NH}}_3$ is:

$\mathrm{HCl}\left(\mathrm{g}\right)+{\mathrm{NH}}_3\left(\mathrm{g}\right)\to {\mathrm{NH}}_4\mathrm{Cl}\left(\mathrm{g}\right)$

Final Answer: Hence, option (A) is correct. $\mathrm{HCl}$ gas is evolved.