(a)
(i) The gas evolved is hydrogen chloride (HCl) gas.
(ii)
Conclusion: HCl gas is acidic in nature. It shows acidic character only in the presence of water (moisture), as it dissolves in water to form hydrochloric acid (H⁺ ions). In dry state, it does not ionise and hence shows no acidic behaviour.
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The key concept here is that HCl is a covalent compound and shows acidic nature only when dissolved in water — it ionises to give H⁺ ions only in the presence of moisture. Dry litmus test vs. wet litmus test distinguishes this beautifully. Examiners expect you to state both observations clearly and draw a conclusion about the role of water in acidic behaviour. This is a standard practical-based question from the Acids, Bases and Salts chapter (Chapter 2).