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 the ester.


(i) Average rate of reaction over interval is [change in concentration]/[time taken] i.e.


(ii) the pseudo first-order rate constant can be calculated by


K = (2.303/t) log(Ci/Ct) where K is Rate constant,


t is time taken,


Ci is initial concentration


Ct is Concentration at time t.


K = (2.303/30) log (0.55/0.31)


K = 1.9 × 10-2 sec-1


(i) Average rate between 30 to 60 sec is 0.00467 mol L-1sec-1


(ii) Pseudo first order rate constant is 1. × 10-2sec-1


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