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

t/s | 0 | 30 | 60 | 90 |

[Ester]/mol L | 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(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 ^{-1}sec^{-1}__

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

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