Write the balanced equation for the following chemical reactions.

(i) Hydrogen + Chlorine ⟶ Hydrogen chloride

(ii) Barium chloride + Aluminium sulphate ⟶ Barium sulphate + Aluminium chloride

(iii) Sodium + Water ⟶ Sodium hydroxide + Hydrogen

Write a balanced chemical equation with state symbols for the following reactions.

(i) Solutions of barium chloride and sodium sulphate in water react to give insoluble barium sulphate and the solution of sodium chloride.

(ii) Sodium hydroxide solution (in water) reacts with hydrochloric acid solution (in water) to produce sodium chloride solution and water.

A solution of a substance 'X' is used for whitewashing.

(i) Name the substance 'X' and write its formula.

(ii) Write the reaction of the substance 'X' named in (i) above with water.

Why is the amount of gas collected in one of the test tubes in Activity 1.7 double of the amount collected in the other? Name this gas.