Give reasons for the following:
(i) We are lucky that ozone is not stable near Earth's surface.
(ii) The combustion of fossil fuels increases the amount of suspended particles in air.

We are lucky that ozone is not stable near to the Earth's surface. Why? Gie appropriate answer.

(a) Give reasons for the following: (i) The sky appears to be blue during day time to a person on earth. (ii) The sky near the horizon appears to have a reddish hue at the time of sunset and sunrise. (iii) The sky appears dark instead of blue to an astronaut. (iv) The stars appear to twinkle. (v) The planets do not twinkle.

Give reasons for the following : (i) Though nitrogen exhibits + 5 oxidation state, it does not form pentahalide. (ii) Electron gain enthalpy with negative sign of fluorine is less than that of chlorine. (iii) The two oxygen-oxygen bond lengths in ozone molecule are identical.

Give reasons for each of the following: (i) Size of trivalent lanthanoid cation decrease with increase in the atomic number. (ii) Transition metal fluorides are ionic in nature whereas bromides and chlorides are usualy covalent in nature. (iii) Chemistry of all the lanthanoids is quite similar.

Give reasons for the followign : (i) Fossil fuels are termed non-renewable resources. (ii) Solar energy is considered inexhaustible resource. (iii) Why is atmosphere considered blanket for living organisms ?

Give reasons for the following: (i) Transition metals exhibit a wide range of oxidation states. (ii) Cobalt (II) is very stable in aqueous solutions but gets easily oxidised in the presence of strong ligands. (iii) Actinoids exhibit a greater range of oxidation states than lanthanoids.