The correct order for increasing the boiling point of hydrides (given below) of group 15 is:
(A) \(NH_3\)
(B) \(PH_3\)
(C) \(AsH_3\)
(D) \(SbH_3\)
(E) \(BiH_3\)
Choose the correct answer from the options given below :
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → B < C < A < D < E
From \( \ce{PH3} \) to \( \ce{BiH3} \) the boiling point rises with molar mass, because the van der Waals forces grow with the size of the molecule. NH3 is out of line: its molecules are held by hydrogen bonds, so it boils higher than \( \ce{PH3} \) and \( \ce{AsH3} \), though below the much heavier \( \ce{SbH3} \) and \( \ce{BiH3} \).
Note 1: This question is from the pre-rationalised NCERT book (2022-23). The topic is not there in the latest NCERT book (2026-27), and it is also out of the CUET 2026 syllabus.
NCERT (Pre-rationalised edition, 2022-23):
Reactivity towards Hydrogen – …
Note 2: The same/similar question has been asked in different years by NTA as per the details given below:
| 2026 | 2025 | 2024 | 2023 | 2022 |
|---|---|---|---|---|
| – | – | – | 28-05 S1 24-05 S3 | – |