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JEE Chemistry · Medium

Chemical Kinetics: Pseudo-first order MCQ

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Pseudo-first orderMediumQuestion 720009

Question

The acid hydrolysis of ester in excess water follows pseudo-first order because:
  1. A
    Water concentration is nearly constant
    Correct
  2. B
    Rate depends on ester alone
  3. C
    Activation energy is zero
  4. D
    The reaction is elementary

Correct answer

Water concentration is nearly constant

Explanation

In dilute solution, water is in large excess and its concentration barely changes during reaction. The rate law r = k[ester][H₂O] ≈ k'[ester] where k' = k[H₂O] is approximately constant. Hence pseudo-first order.

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