Question

Experiment	A	B	C	intial rate of formation of D (M/min)
1	2.0	2.0	2.0	2.0
2	2.0	1.0	2.0	2.0
3	4.0	5.0	2.0	8.0
4	2.0	4.0	1.0	1.0
5	3.0	4.0	4.0	?

a) Determine the rate law.

b) Calculate the rate constant. Specify units.

c) Calculate the rate of reaction for experiment 5.

d) How is the rate of appearance of D related to the disappearance of B?

e) In experiment 3, what is the rate of disappearance of B?

Answer 1

Let the rate expression be r_D= K[A]^m [ B]ⁿ [C]^p

2.0 2.0             2.0 2.0                             

where   m,n,p are orders with respect to A, B, C respectively and K is rate constant

from First experiments

2= K [2]^m [2^]n [2]^p     (1)

From second experiment

2= K [2]^m [1^]n [2]^p     (2)

Dividing 1 and 2 gives

1= 2ⁿ   , n= 0

The rate expression becomes r_D= K[A]^m [C]^p

from 3rd experiment   8=K [ 4]^m [2]^p    (3)

dividing 3 and 1 gives

4= (4/2)^m ,     m= 2

From experiment 4

2.0            4.0             1.0 1.0

1= K[ 2]² [ 1]^p     (4)

Dividing 4 and 1 gives

2= [2]^p   , p= 1

From 1

2= K[2]² [ 2]¹ K= 0.25

The rate expression then becomes

rD= 0.25 [ A]² [C]¹

The units of rate constant can be seen as

M/sec= Rate constant* [M]³

M= molarity

Rate constant = /M².sec

following data refer to the reaction: A + 2B + C --> D + 2E

for the last experiment where A= 3 and C= 4

r^D= 0.25*[3]2*4= 0.25*9*4= 9M/sec

A + 2B + C --> D + 2E

-rB/2= rD/1

Where 2 and 1 are coefficients of B and D in the reaction

In the 3rd experiments

-rB/2= rD/1= 8

-rB= 16 M/Sec.