Class 12 Chemistry - Chapter Chemical Kinetics NCERT Solutions | In a pseudo first order hydrolysis of es

Welcome to the NCERT Solutions for Class 12th Chemistry - Chapter Chemical Kinetics. This page offers a step-by-step solution to the specific question from Exercise 2, Question 8: in a pseudo first order hydrolysis of ester in wat....
Question 8

In a pseudo first order hydrolysis of ester in water, the following results were obtained:

t/s 0 30 60 90

[Ester]mol L - 1

0.55 0.31 0.17 0.085

(i) Calculate the average rate of reaction between the time interval 30 to 60 seconds.

(ii) Calculate the pseudo first order rate constant for the hydrolysis of ester.

Answer

(i) Average rate of reaction between the time interval, 30 to 60 seconds, = d[ester] / dt

= (0.31-0.17) / (60-30)

= 0.14 / 30

= 4.67 × 10 - 3mol L - 1s - 1

 

(ii) For a pseudo first order reaction,

k = 2.303/ t log [R]º / [R]

For t= 30 s, k1 = 2.303/ 30 log 0.55 / 0.31

= 1.911 × 10 - 2s - 1

For t = 60 s, k2 = 2.303/ 60 log 0.55 / 0.17

= 1.957 × 10 - 2s - 1

For t= 90 s, k3 = 2.303/ 90 log 0.55 / 0.085

= 2.075 × 10 - 2s - 1

Then, average rate constant, k = k1 + k2+ k/ 3

= 1.911 × 10 - 2  + 1.957 × 10 - 2 + 2.075 × 10 - 2 / 3

= 1.981 x 10-2 s - 1

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