Question

Choose the correct order of the following :

• A. $N-H>P-H>As-H>Sb-H\text{: Polarity order}$
  
• B. $M{g}^{2+}\left(aq\right)>S{r}^{2+}\left(aq\right)>B{a}^{2+}\left(aq\right)\text{: Hydrated radius order}$
  
• C. $M{g}^{2+}\left(aq\right)>S{r}^{2+}\left(aq\right)>B{a}^{2+}\left(aq\right)\text{Ionic mobility order}$
• D. $NaF>MgO>SrO\text{: Lattice energy order}$

Answer 1

The correct option is B $M{g}^{2+}\left(aq\right)>S{r}^{2+}\left(aq\right)>B{a}^{2+}\left(aq\right)\text{: Hydrated radius order}$


(A) Polarity increases as electronegativity difference increases . But electronegativity of (P) $\approx$ electronegativity of (H). So the correct order of polarity is
$N-H>As-H>Sb-H>P-H$

(B) Lesser is the size of the cation, more is the hydration and hence more is the hydrated radius. So the correct order for hydrated radius is: $M{g}^{2+}\left(aq\right)>S{r}^{2+}\left(aq\right)>B{a}^{2+}\left(aq\right)$

(C) Lesser is the size of the cation, more is the hydration and hence lesser mobility. So the correct order for ionic mobility is: $M{g}^{2+}\left(aq\right)<S{r}^{2+}\left(aq\right)<B{a}^{2+}\left(aq\right)$

(D) Lattice energy depends on the charge of cation and anion and their internuclear distance. More is the charge and lesser is the internuclear distance, greater is the lattice energy Thus the correct order is $MgO>SrO>NaF$