Question

Consider the reaction

A+2B⇌C

whose rate at 25 ∘C was measured using three different sets of initial concentrations as listed in the following table:

Calculate the initial rate for the formation of C at 25 ∘C, if [A]=0.50M and [B]=0.075M.

Express your answer to two significant figures and include the appropriate units.

Trial	[A] (M)	[B] (M)	Rate (M/s)
1	0.35	0.010	1.5×10−3
2	0.35	0.020	2.9×10−3
3	0.70	0.010	5.9×10−3

Answer 1

1st we need to find the arte law

Let the rate law be written as
rate = K [A]^x * [B]^y

consider trial 1 and trial 2 , here [A] is same.
[B] doubles and rate also doubles approximately
So y=1

consider trial 1 and trial 3 , here [B] is same.
[A] doubles and rate becomes 4 times approximately
So x=2

so,
above arte law becomes,
rate = K [A]^2 * [B]
put the values from trial 1 to find K
rate = K [A]^2 * [B]
1.5*10^-3 = K *(0.35)^2 * (0.01)
K = 1.22

SO rate law is
rate = 1.22 * [A]^2 * [B]

put [A] = 0.50 M and [B] = 0.075 M

rate = 1.22 * [A]^2 * [B]
           = 1.22 * (0.5)^2 * (0.075)
           = 0.023 M/s
Answer: 0.023 M/s