(a) Account for the following: (i) Tendency to show -3 oxidation state decreases from $\mathrm{N}$ to $\mathrm{Bi}$ in group 15. (ii) Acidic character increases from $\mathrm{H}_2\mathrm{O}$ to $\mathrm{H}_2\mathrm{Te}$. (iii) $\mathrm{F}_2$ is more reactive than $\mathrm{CIF}_3$, whereas $\mathrm{CIF}_3$ is more reactive than $\mathrm{Cl}_2$. (b) Draw the structure of (i) $\mathrm{XeF}_2$ (ii) $\mathrm{H}_4\mathrm{P}_2\mathrm{O}_7$. OR (a) Give one example to show the anomalous reaction of fluorine. (b) What is the structural difference between white phosphorus and red phosphorus? (c) What happens when $\mathrm{XeF}_6$ reacts with $\mathrm{NaF}$ ? (d) Why is $\mathrm{H}_2\mathrm{S}$ a better reducing agent than $\mathrm{H}_2\mathrm{O}$ ? (e) Arrange the following acids in the increasing order of their acidic character: $\mathrm{HBr}, \mathrm{Hl}, \mathrm{HCl}, \mathrm{HF}$