Considering the parameters such as bond dissociation enthalpy,electron gain enthalpy and hydration enthalpy, compare the oxidising power of `F_(2)` and `Cl_(2)`.

Explanation

(i) Comparing `F_(2) and Cl_(2)` with the given parameters.

From the data given above, it is clear that the bond dissociation enthalpy and electron gain enthalpy are higher for chlorine but hydration energy is much higher for fluorine.
It compensates the effect of other two and thus makes fluorine more oxidising than chlorine.
`(1)/(2)X_(2)(g)overset(1//2Delta_("diss")H^(@))(to)X(g)overset(Delta_(e)""_(g)H^(@))(to)X^(-)(g)overset(Delta_(hyd)H^(@))(to)X^(-)(ag)`
The relative oxidising power of the halogens can be further illustrated by their reactions with water.
`2F_(2)(g)+2H_(2)O(l)to4H^(+)(aq)+4F^(-)(aq)+O_(2)(g)`
`Cl_(2)(g)+H_(2)O(l)toHCl(aq)+HOCl(aq)`
(ii) The colour of halogens is due to the absorption of light in the visible region. As a result, electrons get excited to higher energy level and the compound exhibits colour.