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.

Question

Philoid · Accepted Answer

(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(C_i/C_t) where K is Rate constant,

t is time taken,

C_i is initial concentration

C_t 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