a. Give reasons for the following:
(i) Sulphur in vapor state shows paramagnetic behavior.
(ii) N-N bond is weaker than P-P bond.
(iii) Ozone is thermodynamically less stable than oxygen.

b. Write the name of gas released when Cu is added to
(i) dilute HNO₃ and
(ii) conc. HNO₃

OR

(a) (i) Write the disproportionation reaction of H₃PO₃.
      (ii) Draw the structure of XeF₄.
(b) Account for the following:
(i) Although Fluorine has less negative electron gain enthalpy yet F₂ is strong oxidizing agent.
(ii) Acidic character decreases from N₂O₃ to Bi₂O₃ in group 15.
(c) Write a chemical reaction to test sulphur dioxide gas. Write chemical equation involved.

a. (i) Sulphur partly exist as S₂  in vapour state. It has 2 unpaired electrons which make it paramagnetic.
    (ii) N has small size as compared to P. Due to which N-N bond inter-electronic repulsion is more. Therefore, N-N bond weaker than P-P bond.
   (iii) The decomposition of ozone leads to formation of oxygen. In this process large amount of heat is liberated with increase in entropy. It results into large negative Gibbs free energy change. Therefore, ozone is thermodynamically less stable.

b. (i) Nitric oxide
    (ii) Nitrogen dioxide

OR

(a) (i) ${\mathrm{H}}_3{\mathrm{PO}}_3\to 3{\mathrm{H}}_3{\mathrm{PO}}_4+{\mathrm{PH}}_3$
(ii)
(b) (i) Fluorine has small size low bond dissociation enthalpy which makes it a strong oxidizing agent.
(ii) On going down the group the size of elements increases. It decreases the electronegativity. Due to which acidic character decreases.
(c) $5{\mathrm{SO}}_2+2{\mathrm{MnO}}_4^{-}+2{\mathrm{H}}_2\mathrm{O}\to 5{\mathrm{SO}}_4^{2-}+4{\mathrm{H}}^{+}+2{\mathrm{Mn}}^{2+}$