Question

The electronegativity of halogens decreases from fluorine to iodine while the electron affinity has the trend $Cl>F>Br>I$. The halogens are good oxidizers The oxidizing power of halogens in aqueous medium depends on their electron affinity, bond dissociation energy and heat of hydration. Basic character of their anions depends on their size and electronegativity. Similarly, the ionic character of the salts of different halides of the same metal depends on their electronegativity and size.

The heat of hydration and the basic character of halide ions follow the order:

• A. $C{l}^{-}>F^{-}>Br->I^{-}$
• B. $F^{-}>C{l}^{-}>B{r}^{-}>I^{-}$
• C. $I^{-}>B{r}^{-}>F^{-}>C{l}^{-}$
• D. $I^{-}>B{r}^{-}>C{l}^{-}>F^{-}$

Answer 1

The correct option is B $F^{-}>C{l}^{-}>B{r}^{-}>I^{-}$

Smaller the size, greater will be the hydration. Also the strongest acid has the weakest conjugate base. Thus $F^{-}$ the smallest ion is most readily hydrated (maximum hydration energy is released). HF is the weakest acid, so$F^{-}$ is the strongest base and $I^{-}$ is the weakest base. Hence the order $F^{-}>C{l}^{-}>B{r}^{-}>I^{-}$.