Suppose you have measured the kinetics of the reaction, 2 A + B → C + 2 D at room temperature using the method of initial rates.

Question

A table summarizing the results of four different experimental trials is shown below:

Experimental	Initial A	Initial B	Initial rate
Trial	(M)	(M)	(M s-1)
1	0.15	0.30	0.000857
2	0.30	0.30	0.001714
3	0.15	0.15	0.000428
4	0.45	0.45	0.003856

You conclude that the reaction is first order in [A] and first order in [B].

Based on these data, what is the value of the rate constant k (in units of  M^-1 s^-1).



{Enter your value with three significant figures.}

Answer 1

First order in A and B:

Rate = k[A][B]

Using data from trial 1 (you can use any trial), we have...

0.000857 Ms^-1 = k[0.15][0.30] = 0.045 M² * k

Solving for k, we have...

k = 0.000857 Ms^-1 / 0.045 M²

k =0.0190 M^-1s^-1