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Question #44172

Difficulty: 8/10 | 🟢 Free

The Question

Consider the trihalides \ce{PF3} and \ce{PCl3} at $298\text{ K}$ . Based on Bent's rule and the principles of hybridization, which of the following sets of statements correctly describes their structural and chemical properties?

(I) The lone pair on the phosphorus atom in \ce{PF3} occupies an orbital with a higher fractional s-character than the lone pair in \ce{PCl3}. (II) The $X-P-X$ bond angle is smaller in \ce{PF3} than in \ce{PCl3}. (III) \ce{PF3} is a stronger $\sigma$ -donor (Lewis base) towards hard Lewis acids than \ce{PCl3} because fluorine causes less steric hindrance than chlorine. (IV) In transition metal complexes, \ce{PF3} acts as a stronger $\pi$ -acceptor ligand than \ce{PCl3}.

Options

A.
I, II, and IV only
B.
I, III, and IV only
C.
II, III, and IV only
D.
I and II only

Check Your Answer

Correct Answer

Step-by-Step Solution

Explanation

How the Examiner Thinks

Mechanism_Trap

Don't get tricked by the process! Learn the mechanical traps used in competitive exam questions.

Concepts Behind This Question

Hybridization in Non-Standard Cases|Electrophile vs Nucleophile|C-X Bond Polarization and Polarizability

Why This Question Is Tricky

Common Mistakes

The problem tests the deep implications of Bent's Rule beyond simple bond angles.

Students often fall into the trap of assuming that all $sp^3$ hybridized molecules have identical lone pair characters.

By linking the electronegativity of the substituent to the s-character of the lone pair, the question explores how this hidden variable dictates Lewis basicity.

A common misconception is that \ce{PF3} should be a better Lewis base due to lower steric hindrance from the smaller fluorine atoms, ignoring the dominant electronic effect where the high s-character of the lone pair makes it tightly bound and unavailable for $\sigma$ -donation.

Quick Facts About This Question

Question Information

Subject	Chemistry
Chapter	Chemical Bonding and Molecular Structure - Class 11 Part 1
Concept	Hybridization in Non-Standard Cases
Difficulty	8
Cognitive Load	7
Target Solve Time	160 sec
Access	Free