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Question #44827
The Question
The acid-catalyzed hydration of 1-methylcyclohexene to 1-methylcyclohexanol proceeds via a rate-determining protonation step. In pure water at (viscosity ), the reaction exhibits an activation energy and a rate constant .
To study solvent-solute dynamics, the reaction is transferred to a highly viscous glycerol-water mixture. In this medium, the dielectric constant remains identical to water, but the kinetics enter the Kramers high-friction regime. According to Kramers' theory, the Arrhenius pre-exponential factor becomes inversely proportional to the solvent viscosity () due to the Franck-Rabinowitch caging effect.
At , the viscosity of the glycerol-water mixture is . Assuming remains strictly constant across both media, what is the ratio of the rate constant in the viscous mixture at () to ?
(Given: , )
Options
- A.
5.0
- B.
10.0
- C.
20.0
- D.
1.0
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
Arrhenius Pre-exponential Factor|Acid-Catalyzed Hydration Mechanism
Why This Question Is Tricky
Common Mistakes
This question tests the 'Chemical Exception' to the standard Arrhenius equation where the pre-exponential factor (A) is assumed constant.
In high-viscosity solvents, the reaction enters the Kramers high-friction regime, where the collision frequency drops due to the 'caging effect' (Franck-Rabinowitch effect).
Students must integrate this inverse viscosity dependence () with the standard temperature-dependent exponential term.
A common trap is ignoring the solvent's effect on A (yielding 10.0) or misapplying the proportionality as direct instead of inverse (yielding 20.0).
Quick Facts About This Question
Question Information
| Subject | Chemistry |
| Chapter | Chemical Kinetics - Class 12 |
| Concept | Arrhenius Pre-exponential Factor |
| Difficulty | 8 |
| Cognitive Load | 7 |
| Target Solve Time | 160 sec |
| Access | Free |