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Question #44344
The Question
Consider the halomethanes \ce{CH3F} (Molecule 1) and \ce{CH3I} (Molecule 2) at 298 K. Let represent the fractional s-character of the carbon hybrid orbital directed towards the halogen atom, represent the fractional p-character of the carbon hybrid orbital directed towards a hydrogen atom, and represent the H-C-H bond angle. Assuming molecular geometry is strictly governed by electronic orbital rehybridization (Bent's Rule) and neglecting steric repulsion, which of the following correctly represents the relationship between these parameters for the two molecules?
Options
- A.
; ;
- B.
; ;
- C.
; ;
- D.
; ;
Check Your Answer
Correct Answer
Step-by-Step Solution
Explanation
How the Examiner Thinks
Exception_Exposure
Learn to identify edge cases and boundary exceptions that JEE examiners hide in math problems.
Concepts Behind This Question
Bent's Rule|C-X Bond Polarization and Polarizability|Hybridization and Geometry
Why This Question Is Tricky
Common Mistakes
This question targets the 'Chemical Exception' where students assume all hybridized carbons have identical bond angles and 25% s-character per bond (simple VSEPR theory).
The hidden variable is the redistribution of s and p character driven by substituent electronegativity (Bent's Rule).
Students often fall into the trap of either ignoring this rehybridization or incorrectly assuming that a larger halogen (Iodine) will sterically force a larger H-C-H angle.
By explicitly constraining the problem to electronic effects, it forces the student to trace the conservation of orbital character: highly electronegative F steals p-character, leaving s-character for the C-H bonds, which consequently opens up the H-C-H angle.
Quick Facts About This Question
Question Information
| Subject | Chemistry |
| Chapter | Chemical Bonding and Molecular Structure - Class 11 Part 1 |
| Concept | Bent's Rule |
| Difficulty | 8 |
| Cognitive Load | 7 |
| Target Solve Time | 160 sec |
| Access | Free |