Question: 69: Flourine is a stronger oxidising agent than chlorine because :
(a) F-F bond has a low enthalpy of dissociation.
(b) Flouride ion \left(\mathrm{F}^{-}\right)has high hydration enthalpy.
(c) Electron gain enthalpy of flourine is less negative than chlorine.
(d) Flourine has a very small size.
Choose the most appropriate answer from the options given :
(1) ) (a) and (b) only
(2) (a) and (c) only
(3) (a) and (d) only
(4) (b) and (c) only
Answer: Option (1)
Explanation:
Oxidising power of an element depends on its tendency to gain electrons and get reduced.
Fluorine shows exceptionally high oxidising power compared to chlorine due to
energetic factors involved in the overall reduction process.
The F–F bond has very low bond dissociation enthalpy because of strong repulsion
between lone pairs on the small fluorine atoms.
Due to this low bond enthalpy, fluorine molecules easily dissociate to form fluorine atoms,
which readily accept electrons.
The fluoride ion \mathrm{F}^{-} has very high hydration enthalpy
because of its very small size and high charge density.
High hydration enthalpy releases a large amount of energy,
stabilising the fluoride ion strongly in aqueous solution.
Although the electron gain enthalpy of fluorine is less negative than that of chlorine,
the effects of low F–F bond enthalpy and high hydration enthalpy dominate.
Therefore, statements (a) and (b) correctly explain why fluorine is a stronger oxidising agent than chlorine.
Hence, option (1) is the correct answer.