Question

Name the acid used for the preparation of hydrogen chloride gas in the laboratory. Why is this particular acid preferred to other acids?

Write the balanced chemical equation for the laboratory preparation of hydrogen chloride gas.

Answer 1

1. Sulphuric acid $\left({\mathrm{H}}_2{\mathrm{SO}}_4\right)$ is used for the preparation of hydrogen chloride gas$\left(\mathrm{HCl}\right)$ in the laboratory. It is preferred over other acids because of the reasons given below:
2. Since the volatility of sulphuric acid $\left({\mathrm{H}}_2{\mathrm{SO}}_4\right)$ is low as compared to hydrogen chloride $\left(\mathrm{HCl}\right)$gas, it becomes easier to collect hydrogen chloride$\left(\mathrm{HCl}\right)$ gas.
3. Due to dehydrating property of sulphuric acid $\left({\mathrm{H}}_2{\mathrm{SO}}_4\right)$, water can be easily removed from hydrogen chloride $\left(\mathrm{HCl}\right)$gas.
4. In the laboratory hydrogen chloride gas $\left(\mathrm{HCl}\right)$is prepared by heating sodium chloride$\left(\mathrm{NaCl}\right)$ with sulphuric acid $\left({\mathrm{H}}_2{\mathrm{SO}}_4\right)$ to a temperature of around $200°\mathrm{C}$.
5. $$\begin{gathered} {\mathrm{H}}_2{\mathrm{SO}}_4+\mathrm{NaCl}\stackrel{<200°\mathrm{C}}{\to }{\mathrm{NaHSO}}_4+\mathrm{HCl} \\ (\mathrm{Sodium}(\mathrm{Hydrogen} \\ \mathrm{chloride})\mathrm{chloride}) \end{gathered}$$