Question

1) A substance A is consumed by a reaction of unknown order. The initial concentration of A is 1 mM, and concentrations at later times are as shown:

Time (min)_________ [A](mM)

0 __________________1

1 __________________0.83

2 __________________0.73

3 __________________0.62

5 ___________________0.5

10 _________________0.28

15 _________________0.21

a) Test whether a first-order or a second-order reaction best fits the data.

b) What is the rate constant for the reaction?

Answer 1

Here a single reactant is consumed that means the reaction is the first order reaction.

The rate constant of first order reaction is

[R₀]= initial concen tration

[R_t]= final concentration

For first case

time t=1min

[R₀]=1

[R_t]=0.83

For 2nd case

time t=2min

[R₀]=1

[R_t]=0.73

For 3rd case

time t=3min

[R₀]=1

[R_t]=0.62

For 4th case

time t=5min

[R₀]=1

[R_t]=0.5

For 4th case

time t=10min

[R₀]=1

[R_t]=0.28

For 4th case

time t=15min

[R₀]=1

[R_t]=0.21

Hence there is a constancy is maintained which indiacate that the reaction is a first oreder reaction.

The rate constant is the mean rate constant after different time interval