JAMB Chemistry 2011 Paper

Concept:The main gas impurity in laboratory-prepared chlorine is hydrogen chloride, which is removed by dissolving it in water.Explanation:Chlorine gas ($\mathrm{Cl_2}$) prepared in the laboratory is often contaminated with $\mathrm{HCl}$ gas.$\mathrm{HCl}$ is very soluble in water, while $\mathrm{Cl_2}$ is only slightly soluble. So, passing the gas through water removes the $\mathrm{HCl}$ impurity.Concentrated $\mathrm{H_2SO_4}$ is used to dry the gas, not to remove the $\mathrm{HCl}$ impurity.Answer:A. $\mathrm{H_2O}$