State one relevant observation for the following: Anhydrous calcium chloride is exposed to air for some time

State one relevant observation for the following: Platinum is added to aqua-regia.

State one relevant observation for the following: When hydrogen sulphide gas is passed through lead acetate solution.

Give reasons for the following: Fused calcium chloride is used in desiccators.

State one relevant observation for each of the following : Barium chloride solution is slowly added to sodium sulphate solution.

State one relevant observation for the following: Action of dilute hydrochloric acid on lead, nitrate solution.

State one relevant observation for the following reaction : Burning of ammonia in air.

State one relevant observation for the following: Nitric oxide comes in contact with atmosphere.

State one relevant observation for the following reaction : Action of dilute Hydrochloric acid on iron (II) sulphide.

State one relevant observation for the following reaction : Action of Sodium hydroxide solution on ferrous sulphate solution.

State relevant observations for the following: Ammonium hydroxide solution is added to zinc nitrate solution in minimum quantity and thien in excess.