a) (i)* Liquid A: Concentrated sulfuric acid* ($\text{H}_2\text{SO}_4$) Solid B: Sodium chloride* ($\text{NaCl}$) (ii) The purpose of concentrated sulfuric acid in the wash bottle is to dry the hydrogen chloride gas by removing any water vapor. Concentrated sulfuric acid is a strong drying agent*. (iii)* The balanced chemical equation for the reaction of A and B is: $$\text{NaCl(s)} + \text{H}_2\text{SO}_4\text{(l)} \longrightarrow \text{NaHSO}_4\text{(s)} + \text{HCl(g)}$$ b) To test for hydrogen chloride gas, bring a glass rod dipped in aqueous ammonia near the gas. Dense white fumes of ammonium chloride will be observed. $$\text{HCl(g)} + \text{NH}_3\text{(g)} \longrightarrow \text{NH}_4\text{Cl(s)}$$ Alternatively, hydrogen chloride gas turns damp blue litmus paper red. c) A physical property of hydrogen chloride is that it is a colorless gas with a pungent smell. It is also denser than air and highly soluble in water. d) Hydrogen chloride gas is used in industry for the production of hydrochloric acid. Hydrochloric acid is then used in various processes such as the pickling of steel and the manufacture of organic compounds. That's 2 down. 3 left today — send the next one.