39. (a) A solution of hydrogen chloride in water is prepared. The following substances are added to separate portions of the solution: S . No. Substances Added Gas evolved Odour 1. Calcium carbonate 2. Magnesium ribbon 3. Manganese (IV) oxide with heating 4. Sodium sulphide Complete the table by writing the gas evolved in each case and its odour.   40. (b) Write equations for: (i) The action of hot, concentrated sodium hydroxide on chlorine.   41. (ii) The reaction of chlorine with excess of ammonia.   42. (iii) The action of chlorine with slaked lime.   43. (c) An experiment showed that in a lead chloride solution, 6.21 g of lead combined with 4.26 g of chlorine. What is the empirical formula of this chloride? (Pb = 207; Cl = 35.5)