1 g of solid sodium chloride is taken in a clean and dry test tube and 2 mL of conc. Suphuric acid is added to it . If the gas evolved is tested first with dry and then with wet blue litmus paper, in which case will the litmus paper change colour? Give reason for your answer. what inference can be drawn about the nature of the evolved gas ? Support your answer with a chemical equation for the reaction.

Explanation

`2NaCl + H_(2)SO_(4)("conc.") to Na_(2)SO_(4) + 2HCl`
Concentrated suphuic acid reacts with sodium chloride to form hydrogen chloride gas. When the gas evolved is tested with dry blue litmus paper then there is no change in the colour of the dry blue litmus paper. This shows that HCl gas does not behave as an acid in the absence of water.
When the gas is tested with wet blue litmus paper then the blue litmus paper turns red. this shows that HCl gas shows acidic behaviour in the presence of water.
Explanation : Dry HCl does not contain any hydrogen ions `(H^(+))` in it , so it does not show acidic behaviour so HCl gas does not change the colour of the dry of the dry blue litmus paper.
When HCl gas it tested with wet blue litmus paper then HCl gas first dissolves in water to form HCl acid solution.
` HCl(g) overset("dissolves")underset(" in water")to HCl(aq)`
` HCl(aq) to H^(+)(aq) + Cl^(-)(aq)`
HCl solution forms hydrogen ions which can turn blue litmus paper to red.
` Or, HCl + H_(2)O to H_(3)O^(+) + Cl^(-)`