Q. 615.0( 1 Vote )

The gas A is used by most of the animals to obtain energy from food by the process of respiration. When A is acted upon by radiation X, it gets converted into another gas B which is 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 prevents 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 Cover the area D of the earth.

(a) What are 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.

Answer :

a) i) The gas A used by animals to obtain energy from food by respiration is Oxygen O2.

ii) The gas B is Ozone O3. Radiations X (ultraviolet) when act on oxygen, convert oxygen to ozone.

b) The layer C is Ozone layer. Gas B i.e. Ozone forms ozone layer in the stratosphere.

c) i) X- Ultraviolet radiations

ii) Y- Sun. Ultraviolet radiations come from the sun

iii) Z- Chlorofluorocarbons. CFC’s are released from refrigerator and air-conditions which are destroying the ozone layer.

d) Ozone hole has been formed over Antarctica’s upper atmosphere.

e) The radiations X i.e. ultraviolet radiations cause skin cancer, when they fall on skin; they destroy the genetic material of the cells, thus resulting in uncontrolled growth of cells. These radiations are also absorbed by the lens of the eyes which leads to formation of free radicals inside the lens that causes cataract over time. Ultraviolet radiations also cause immunosuppression.

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Depletion of ozone is mainly due to

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