NEET Chemistry The p-Block Elements (XII) Questions Solved


(a) With the help of chemical equations explain the principle of contact process in brief for the manufacture of sulphuric acid. (No diagram)

(b) Account for the following :

(i)  Bond dissociation energy of F2 is less than that of Cl2.

(ii) Nitric oxide (NO) becomes brown when released in air.

(a) Principle of contact process : The process involves the oxidation of sulphur dioxide by air in the presence of a catalyst.


Sulphur trioxide is dissolved in 98% H2SO4 acid and oleum is formed

 H2SO4+SO3H2S2O7 oleum

Oleum is diluted with water to form sulphuric acid


(b) (i) The low bond dissociation energy of F is due to high inter electronic repulsions between non-bonding electrons in 2p-orbitals as the size of F atoms is small. As a result, F-F bond is weaker than Cl-Cl bond.

(ii) It readily combines with O2 to form brown fumes of NO2.

     2NO+O22NO2brown fumes


Difficulty Level: