What do you observe when silver nitrate is added to a solution of sodium chloride?

What do you observe when ferrous sulphate solution is added to an aqueous solution of sodium hydroxide?

What do you observe when dilute sulphuric acid is added to barium chloride solution?

State the conditions required for the following reactions to occur :

(a) Decomposition of water into hydrogen and oxygen.

(b) Formation of iron sulphide from iron and sulphur.

(c) Reaction between zinc and dilute hydrochloric acid to produce hydrogen gas.

(d) Decomposition of potassium chlorate into potassium chloride and oxygen.