1. (i) Name the acid formed when sulphur dioxide dissolves in water.   2. (ii) Name the gas released when sodium carbonate is added to a solution of sulphur dioxide.   3. (iii) What are the two necessary conditions for the direct combination of sulphur dioxide and chlorine forming sulphuryl chloride?   4. (iv) State the property of sulphur dioxide which causes potassium permanganate to change its colour from purple to colourless.