(a) Give reasons : (i) Helium does not form compounds like Xenon. (ii) HClO_(4) is a stronger acid than HOCl. (iii) PCl_(5) acts as an oxidising agent. (b) Write one reaction as an example of each, to show that conc. H_(2)SO_(4) acts as (i) an oxidising agent, and (ii) a dehydrating agent.

(a) Give reasons : (i) Helium does not form compounds like Xenon. (i

1.	(a) Give reasons : (i) Helium does not form compounds like Xenon. (ii) HClO_(4) is a stronger acid than HOCl. (iii) PCl_(5) acts as an oxidising agent. (b) Write one reaction as an example of each, to show that conc. H_(2)SO_(4) acts as (i) an oxidising agent, and (ii) a dehydrating agent.
Answer» Solution :(a) (i) Helium being small in size has a very large value of ionisation enthalpy `(2372" kJ mol"^(-1))`. It has, THEREFORE, no tendency for compound FORMATION. Xenon, on the other hand, has ionisation enthalpy of `1170" kJ mol"^(-1)`. Therefore it can form compounds. (ii) Oxidation number of Cl in `HClO_(4)` is +7 and that of Cl in HClO is +1. Greater the oxidation number, greater is the strength of the acid. (iii) `PCl_(5)` acts as an oxidising agent because oxidation number of phosphorus is decreased in the reaction. Consider the following reaction `2Ag+PCl_(5)to2AgCl+PCl_(3)` `PCl_(5)` has been REDUCED to `PCl_(3)`, thus it has acted as an oxidising agent. (b) (i) `Cu+2H_(2)SO_(4)overset("conc.")toCuSO_(4)+SO_(2)+2H_(2)O` (ii) `underset("Sucrose")(C_(12)H_(22)O_(11))overset(H_(2)SO_(4))to12C+11H_(2)O`