Name the gas produced when:

(a) steam is passed over hot coke.

(b) chlorine is dissolved in water and exposed to sunlight.

(c) a piece of calcium is added to water.

(d) when fossil fuel is burnt.

Define:

(a) Soft water

(b) Hard water

Suggest one method for the removal along with the reactions for

(i) temporary hardness

(ii) permanent hardness of water

What are the main causes of water pollution? How can it be controlled?