Question

(a) Give reasons for the following :
(i) Sulphur in vapour state shows paramagnetic behaviour.
ii) N-Nbond 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 $HN{O}_3$ and (ii) conc. $HN{O}_3$

Answer 1

(a) (i) Sulphur in vapour state has two unpaired electrons like oxygen in pi antibonding molecular orbital and hence it is paramagnetic.
(ii) $N-N$ single bond is unstable because of small size of 2p orbital hence very strong repulsion as compared to $P-P$
(iii)Ozone is thermodynamically less stable than oxygen because its decomposition into oxygen results in the liberation of heat and we know that entropy is increased and thus Gibb's free energy becomes more negative.

(b)(i) $3Cu+\underset{\left(\text{Dilute}\right)}{8HN{O}_3}⟶\underset{\left(\text{Copper nitrate}\right)}{3Cu{\left(N{O}_3\right)}_2}+4H_{2}O+\underset{\left(\text{Nitric oxide}\right)}{2NO}$
so IUPAC name is Nitrogen monoxide
(ii)
$Cu+4HN{O}_3\to Cu(N{O}_3{)}_2+2N{O}_2+2H_{2}O$
so the IUPAC name is Nitrogen dioxide