For the hydrolysis of methyl acetate in aqueous solution, the following results were obtained:
|
t/s |
0 |
30 |
60 |
|
[CH3COOCH3] / mol L–1 |
0.60 |
0.30 |
0.15 |
(i) Show that it follows pseudo-first order reaction, as the concentration of water remains constant.
(ii) Calculate the average rate of reaction between the time intervals 30 to 60 seconds.
(Given log 2 = 0.3010, log 4 = 0.6021)
For the hydrolysis of methyl acetate to be a pseudo first-order reaction, the reaction should be first order with respect to ester when [H2O] is constant. The rate constant k for a first order reaction is given by:
Where,
[R]0 = intial concentration of reactant
[R] =final concentration of reactant
At =30s
We have
: 
It can be seen that the rate constant k for the reaction has a constant value under any given time interval .Hence the given reaction follows pseudo-first order kinetics.
(ii) Average rate of reaction between the time interval 30-60 seconds is given by
Average rate = 
