The gas A is used by most of the animals to obtain energy from food through the process of respiration. When A is acted upon by radiation X, it gets converted into another gas B which an allotrope of A but poisonous when inhaled. B forms a kind of layer C in the upper atmosphere which absorbs radiations X coming from a source Y and prevent them from reaching the earth. Some chemicals Z released from the various devices on the earth are destroying the layer C slowly. In fact, a hole has already been formed in layer C over the area D of the earth.

(a) What are the gases (i) A, and (ii) B? Write their molecular formulae.

(b) Name the layer C.

(c) What are (i) X, (ii) Y, and (iii) Z?

(d) Name the area D.

(e) Name any two human ailments which may be caused by X.

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Solution

(a) (i) A is oxygen $(O_{2})$ , and (ii) B is ozone $(O_{3})$ .

(b) C is the ozone layer.

(c) (i) X is ultraviolet (UV) radiations.
(ii) Y is the sun.
(iii) Z is chlorofluorocarbons (CFCs).

(d) D is Antarctica.

(e) Skin cancer and cataract are two human ailments that may be caused by X (ultraviolet radiations).

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