Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R).
Assertion (A) : has lower boiling point than .
Reason (R) : In liquid state molecules are associated through vander waal's forces, but molecules are associated through hydrogen bonding.
In the light of the above statements, choose the most appropriate answer from the options given below:
Assertion (A) : has lower boiling point than .
Reason (R) : In liquid state molecules are associated through vander waal's forces, but molecules are associated through hydrogen bonding.
In the light of the above statements, choose the most appropriate answer from the options given below:
- (A)Both (A) and (R) are correct and (R) is not the correct explanation of (A)
- (B)(A) is not correct but (R) is correct
- (C)Both (A) and (R) are correct but (R) is the correct explanation of (A)
- (D)(A) is correct but (R) is not correct✓ Correct
Answer: (D)
Solution
In liquid NH, molecules associate through hydrogen bonding (N-H...N), which requires extra energy to break during vaporisation, giving NH a relatively high boiling point. PH molecules, on the other hand, do not hydrogen-bond appreciably (P is less electronegative and the atom is larger) and are held together mainly by weak van der Waals forces, giving PH a lower boiling point. So Assertion (A) — PH has a lower boiling point than NH — is correct, but Reason (R), which swaps which gas shows which type of association (it claims NH is held by van der Waals forces and PH by hydrogen bonding), is incorrect. So (A) is correct but (R) is not correct.
JEE Main · 2024 · 01 Feb 2024 · Shift 1 · Single correct option