Question

Select the correct satement(s)

• A. Compared to $M{e}_{3}N,(Si{H}_3{)}_{3}N$ has got almost no basicity.
• B. The molecular formulas of nitrogen and phosphorus are $N_2$ and $P_4$ respectively ; similarly, oxygen exists as $O_2$ while sulphur exists as $S_8$
• C. The dipole moment of $R_{3}NO$ is much greater comared to that of $R_{3}PO$.
• D. All the $B-O$ bond lengths are not identical in polyborates.

Answer 1

Answer: (A), (B), (C), (D)

The correct options are
A Compared to $M{e}_{3}N,(Si{H}_3{)}_{3}N$ has got almost no basicity.
B The dipole moment of $R_{3}NO$ is much greater comared to that of $R_{3}PO$.
C All the $B-O$ bond lengths are not identical in polyborates.
D The molecular formulas of nitrogen and phosphorus are $N_2$ and $P_4$ respectively ; similarly, oxygen exists as $O_2$ while sulphur exists as $S_8$

(A) Compared to $M{e}_{3}N,(Si{H}_3{)}_{3}N$ has got almost no basicity.
This is because, in trisilyl amine, the lone pair on $N$ is involved in pi bond formation with $Si$ whereas in trimethyl amine, the lone pair is free.
Thus, the option A is correct.
(B) Nitrogen and phosphorus forms dimer and tetramer whereas oxygen and sulphur forms dimer and octamer.
Hence, the molecular formulas of nitrogen and phosphorus are $N_2$ and $P_4$ respectively ; similarly, oxygen exists as $O_2$ while sulphur exists as $S_8$
Thus, the option B is correct.
(C) The dipole moment of $R_{3}NO$ is much greater compared to that of $R_{3}PO$.
This is because, in case of $R_{3}NO$, all the individual bond dipoles reinforce each other which is not the case for $R_{3}PO$.
Thus, the option C is correct.
(D) All the $B-O$ bond lengths are not identical in polyborates.
Hence, the option D is correct.