(a) Complete the following chemical equation :
(i)
Cu+HNO3(dil.)→ (ii)
XeF4+O2F2→(b) Explain the following observations :
(i) Phosphorus has a grater tendency for catenation than nitrogen.
(ii) Oxygen is a gas but sulphur a solid.
(iii) The halogens are coloured. Why?