Oxidising power of F2 &Cl2
The oxidising powers of both the members of halogen family are expressed in terms of their electron accepting tendency and can be compared with their standard reduction potential values.
F2+2e−→2F−; E∘=2.87 V
Cl2+2e−→2Cl−; E∘=1.36 V
Since, E∘F2/F−→E∘Cl2/Cl− ,F2 is a stronger oxidising agent.
Three factors contribute towards the oxidation potentials of both the halogens.
(i) Bond dissociation enthalpy: Bond dissociation enthalpy of F2(158 kJ mol−1) is less compared to that of Cl2(242.6kJ mol−1)
(ii) Electron gain enthalpy: The negative electron gain enthalpy of F(−332.6 kJ mol−1) is slightly less than of Cl(−348.5 kJ mol−1).
(iii) Hydration enthalpy: The hydration enthalpy of F−ion(515 kJ mol−1) is much higher than that of Cl−ion(381 kJ mol−1) due to its smaller size.
From the available data, we may conclude that lesser bond dissociation enthalpy and higher hydration enthalpy compensate lower negative electron gain enthalpy of fluorine as compared to chlorine.
Consequently, F2 is a more powerful oxidising agent than Cl2.