Explain the following
(i) A little acid is always added in the preparation of aqeous ferrous sulphate solution
(ii) Aqueous solution of mercuric chloride and stannous chloride cannot exist together .
(ii) Ferric iodide is very unstable but ferric chloride is not.
(iv) `Hg^(2+) and Hg_(2)^(2+)` salts are colourless generaly .

Pure HI kept in a bottle axquires a brown colour after sometime. Why? (b) Ferric ioddic is very unstable but ferric chloride is stable. Why? (c ) KHF_(2) is well known but KHCl_(2) and KHBr_(2) do not exist. Why?

State the observations you would make on adding sodium hydroxide to aqueous solution of (i) ferrous sulphate (ii) aluminium chloride.

Mention the products formed in the following (i) Zinc oxide is treated with excess of sodium hydroxide solution (ii). Iodine is added to a solution of stannous chloride.

Account for the following observation and write balanced chemical equations for them. (i). When ferrous sulphate crystals are exposed to air, it turns brown. (ii). A solution of ferric chloride in water gives a brown precipitate on standing.

Which of the following colour change occurs when tridentate ligand, ethane-1, 2-diamine (en) is progressively added to an aqueous solution of nickel (II) chloride ?

What happens when (i)Hydrogen sulphide is bubbled through an aqueous solution of sulphur dioxide. (ii)Hydrogen sulphide is passed through acidified ferric chloride.

Convey the following information in the form of balanced chemical equations (i) An aqueous of ferrous sulphate reacts with an aqueous solution of sodium hydroxide to form precipitate of ferrous hydroxide and sodium sulphate remains in solution. (ii) Potassium metal reacts with water to give potassium hydroxide solution and hydrogen gas is evolved in the reaction. (iii) Solid potassium chlorate upon heating forms potassium chloride and liberates oxygen gas. (iv) An aqueous solution of aluminium chloride reacts with an aqueous solution of ammonium hydroxide solution to form aluminium hydroxide and ammonium chloride.