Question

The following initial rate information was collected at 25^oC for the following reaction:

2H_2(g) + 2NO_(g) --> N_2(g) + 2H₂O_(g)

H2]0 (M)	[NO]0 (M)	Initial Rate (M/min)
0.0010	0.0020	1.2 x 10-4
0.0010	0.0030	1.8 x 10-4
0.0020	0.0020	4.8 x 10-4

Determine the overall order of the reaction and present you answer in numeric form (i.e. 0, 1, 2 etc).

Answer 1

Given reaction is A + B -----------> C + D

rate = k [A]^m [B]ⁿ    k = rate constant

From trial 1,

1.2 x 10^-4 = k [0.001]^m [0.002]ⁿ ------- Eq (1)

From trial 2,

1.8 x 10^-4 = k [0.001]^m [0.003]ⁿ --------Eq (2)

From trial 3,

4.8 x 10^-4 = k [0.002]^m [0.002]ⁿ --------Eq (3)

Do Eq(2)/Eq(1),

(1.8 x 10^-4 /1.2 x 10^-4 ) = (k/k) (0.001/0.001)^m (0.003/0.002)ⁿ

1.5 = 1^m x 1.5ⁿ  

1.5 = 1 x 1.5ⁿ  

Therefore, n =1

Do Eq(3)/Eq(1),

(4.8 x 10^-4 /1.2 x 10^-4 ) = (k/k) (0.002/0.001)^m (0.002/0.002)ⁿ

4 = 2^m x 1ⁿ  

Substitute n=1,

4 = 2^m x 1

4 = 2^m

2² = 2^m

2= m

m = 2

Therefore, m= 2, n= 1

Then,

overall order of the reaction = m + n = 2 +1 = 3