Question

With the experimental data given for the kinetic study of the reaction
A + 2B == AB2, answer the following two questions

Experiment [A] 0 M [B] 0 M Initial velocity formation rate of AB2 (M / min)
1 0.5 1.5 4.2x10-3
2 1.5 1.5 1.3x10-2
3 3.0 3.0 5.2 x10-2

11.-Determine the law of speed for the reaction

Answer: ___________________________

12.- Calculate the value of the kinetic constant

Answer: __________________

Answer 1

Q1.

In order to calculate the rate law expression for a A+B reaction, we need to apply Initial Rates Method.

Note that the generic formula goes as follows:

r = k [A]^a [B]^b

Note that if we got at least 3 sets of point, in which we have A and B constant, then we could use:

r1 / r2 = (k1 [A]1^a [B]1^b) / (k2 [A]2^a [B]2^b)

If we assume K1 and K2 are constant, then K1= K2 cancel each other

r1 / r2 = ([A]1^a [B]1^b) / ( [A]2^a [B]2^b)

Then, order according to [A] and [B]

r1 / r2 = ([A]1/[A2])^a * ([B]1/[B]2)^b

If we get two points in which A1 = A2, then we could get B, and vise versa for A...

From the data shown in YOUR table

(4.2*10^-3)/(1.3*10^-2) = (0.5/1.5)^a

a = ln((4.2*10^-3)/(1.3*10^-2))/ln((0.5/1.5)) = 1

choose points:2 and 3

b order = 0, since ln(1) = 0

then

Rate = k*[A]^2

for k

choose any point

5.2*10^-2 = k*(3^2)

k = (5.2*10^-2)/(9)

k = 0.005777 1/Ms