Question

Choose the correct order of the following properties:

• A. $F{e}^{+3}\left(aq\right)>F{e}^{2+}\left(aq\right):$ Ionic mobility order
• B. $B{r}^{-}\left(aq\right)<C{l}^{-}\left(aq\right)<F^{-}\left(aq\right):$ Hydrated radius order
• C. $B{e}^{2+}<M{g}^{2+}<C{a}^{2+}$ Enthalpies of hydration order
• D. $N>C>H>B:$ Electronegativity order

Answer 1

Answer: (B), (D)

$N>C>H>B:$ Electronegativity order

a) Ionic mobility $\propto \frac{1}{\text{size of the hydrated ion}}$
hydrated size of $F{e}^{3+}$ is larger than $F{e}^{2+}$ in aqueous solution due to more hydration.

b) Smaller the size, greater the extent of hydration and hence greater the size of the hydrated ion.

c) The hydration energy decreases as we move down the group, as the size of the metal ion increases. So the correct order of hydration energy is : $B{e}^{2+}>M{g}^{2+}>C{a}^{2+}$

d) As we move from left to right, effective nuclear charge increases and hence electronegativity increases. Hydrogen has greater electronegativity than B because it has a smaller size.