CE 420/520 Environmental Engineering Chemistry
Problem Set No. 2 – Kinetics
Date due: Oct. 3
1.
Problem 1, page 55
2.
Problem 4, page 55
3.
Problem 6, page 56
4.
Problem 9, page 56
5.
Problem 10, page 57
6.
The following mechanism for the thermal decomposition of ozone has been proposed:
K1
O3
=== > O2 + O0
K2
O0 + O2 == > O3
K3
O0 + O3 == > 2O2
(a) Obtain a rate expression for the decomposition of O 3 in terms of O2 and O3.
(b) The reaction is found experimentally to be 2nd order with respect to O3 and –1 order with O2.
State the conditions which must exist among concentrations and rate constants for your rate
expression to agree with these facts
For CE 520 Students (extra credit for students in CE 420)
7.
Experimental results show that at low temperature, chlorine catalyzed the decomposition of ozone
according to the following rate expression:
d[O3]/dt = k [Cl2]1/2 [O3] 3/2
Equation 0
The reactions can be written as follows:
k1
Initiation:
Cl2 + O3
=== > ClO● + ClO2●
k2
Propagation
ClO2● + O3
=== > ClO3● + O2
k3
ClO3● + O3
== > ClO2● + 2O2
Termination
k4
ClO3● + ClO3● == > Cl2 + 3O2
k5
ClO● + ClO● == > Cl2 + O2
(1)
Based on the reaction equations above, derive the rate mechanism for d[O3]/dt?
(hint = set d[ClO2●]/dt and d[ClO3●]/dt equal to zero {assuming steady state}and
substitute expression for ClO2● and ClO3● into other rate expressions)
(2)
Which reaction (of the above 5) can be assumed to be negligible so that the expression
you have derived will be similar to that obtained experimentally (equation 0)?