pBlock ElementsII 1 Question 44
44. Based on the compounds of group 15 elements, the correct statement(s) is (are)
(2018 Adv.)
(a) $\mathrm{Bi}{2} \mathrm{O}{5}$ is more basic than $\mathrm{N}{2} \mathrm{O}{5}$
(b) $\mathrm{NF}{3}$ is more covalent than $\mathrm{BiF}{3}$
(c) $\mathrm{PH}{3}$ boils at lower temperature than $\mathrm{NH}{3}$
(d) The $\mathrm{N}-\mathrm{N}$ single bond is stronger than the $\mathrm{P}-\mathrm{P}$ single bond
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Solution:
- Statement wise explanation is
(i) Statement (a) $\mathrm{Bi}{2} \mathrm{O}{5}$ is a metallic oxide while $\mathrm{N}{2} \mathrm{O}{5}$ is a non-metallic oxide.
Metallic oxides being ionic are basic in nature while non metallic oxides being covalent are acidic in nature. This confirms more basic nature of $\mathrm{Bi}{2} \mathrm{O}{5}$ in comparison to $\mathrm{N}{2} \mathrm{O}{5}$. Hence, this is a correct statement.
(ii) Statement (b) The electronegativity difference between N(3) and $\mathrm{F}(4)$ is less as compared to the electronegativity difference between $\mathrm{Bi}(1.7)$ and $\mathrm{F}(4)$. More electronegativity difference leads to ionic compounds. Thus, $\mathrm{NF}{3}$ must be more covalent in nature as compared to $\mathrm{BiF}{3}$. Hence, this statement is also correct.
(iii) Statement (c) In $\mathrm{NH}{3}$ intermolecular hydrogen bonding is present, which is altogether absent in $\mathrm{PH}{3}$. Thus, $\mathrm{PH}{3}$ boils at lower temperature than $\mathrm{NH}{3}$. Hence, this is also a correct statement
(iv) Statement (d) Due to smaller size of $\mathrm{N}$ the lone pair-lone pair repulsion is more in $\mathrm{N}-\mathrm{N}$ single bond as compared to $\mathrm{O}-\mathrm{P}$ single bond. This results to weaker $\mathrm{N}-\mathrm{N}$ single bond as compared to $\mathrm{P}-\mathrm{P}$ single bond. Hence, this statement is incorrect.
