Question

Trial	[A]	[B]	Rate (M/s)
1	0.25	0.25	4.0 x 101
2	0.50	0.50	3.2 x 102
3	0.25	1.0	6.4 x 102
4	0.50	0.75	7.2 x 102

a. Find the rate law for the reaction.

b. What is the rate constant (k) with correct units?

c. What would the reaction rate be when the initial concentrations of A and B are 0.75?

Answer 1

First we take trial 1 and 2

Order with respect to A:

We took trial 1 and trial 2.

Rate 2 / rate 1 = [A]2[B]2/[A]1[B]1

3.2*10^2/4.0*10^1=(0.50/0.25)x

8= 2^x

2^3= 2^x

Then x= 3

First we take trial 1 and 3

Order with respect to B:

We took trial 1 and trial 3.

Rate 3 / rate 1 = [A]3[B]3/[A]1[B]1

6.4*10^2/4.0*10^1=(1.0/0.25)y

16= 4^y

4^2= 4^y

Then y= 2

Rate law ; rate = k[A]^3[B]^2

Rate constant;k = rate /[A]^3[B]^2

= 4.0*10^1 M/s / 0.25 M^3 *0.25M^2

= 4.1*10^4 /s .M4

The reaction rate be when the initial concentrations of A and B are 0.75 is calculated as follows:

rate = 4.1*10^4 /s .M4 [0.75 M]^3[0.75 M]^2

= 9.72*10^3 M/s