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Question #44809
The Question
The acid-catalyzed hydrolysis of ethyl acetate () is studied at . In Experiment I, the reaction is carried out in pure water () with as the catalyst and an initial ester concentration of . Under these conditions, the reaction exhibits a half-life of . In Experiment II, the reaction is performed in an inert water-dioxane solvent mixture where , keeping the initial ester and catalyst concentrations identical to Experiment I. Assuming the intrinsic third-order rate constant () remains unaffected by the solvent medium, determine the half-life of the ester in Experiment II and the apparent overall order of the reaction under these new conditions.
Options
- A.
, Apparent first-order
- B.
, Apparent first-order
- C.
, Apparent first-order
- D.
, Apparent second-order
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
First Order Half-Life Independence|Pseudo-First Order Kinetics
Why This Question Is Tricky
Common Mistakes
This question tests the misconception that the half-life of a pseudo-first-order reaction is an absolute constant.
Students often memorize that 'first-order half-life is independent of initial concentration' and erroneously apply this to the solvent/excess reactant in pseudo-first-order kinetics (Option B).
The trap exposes that the pseudo-rate constant embeds the concentration of the excess reagent ().
Changing the solvent composition alters and thus the half-life, even though the reaction remains apparently first-order because water is still in large excess (), invalidating Option D.
Quick Facts About This Question
Question Information
| Subject | Chemistry |
| Chapter | Chemical Kinetics - Class 12 |
| Concept | First Order Half-Life Independence |
| Difficulty | 8 |
| Cognitive Load | 7 |
| Target Solve Time | 160 sec |
| Access | Free |