Question

Using the data in the table, determine the rate constant of the reaction and select the appropriate units.

A+2B⟶C+D

Trial	[A] (M)[A] (M)	[B] (M)[B] (M)	Rate (M/s)
1	0.3900.390	0.3800.380	0.01730.0173
2	0.3900.390	0.7600.760	0.01730.0173
3	0.7800.780	0.3800.380	0.06920.0692

k=

Units

M−1s−1

Answer 1

see experiment 1 and 3:

[A] doubles

[B] is constant

rate becomes 4 times

so, order of A is 2

see experiment 1 and 2:

[A] is constant

[B] doubles

rate is constant

so, order of B is 0

overall order = 2 + 0 = 2

Rate law is:

rate = k*[A]^2

Put values from 1st row of table in rate law

rate = k*[A]^2

1.73*10^-2 = k*0.39^2*0.38^0

k = 0.1137 M-1.s-1

Answer: 0.114 M-1.s-1