Environmental Engineering Reference
In-Depth Information
5.7
2
The decomposition of a species A in air occurs via the following reaction:
A
+
A
→
C.ThepressureofCasafunctionof
t
wasmonitoredinareactor.
t
(min)
p
C
(atm)
0
0
20
0.01
40
0.05
60
0.10
90
0.12
120
0.14
4
0.16
Obtain (i) the order of the reaction, (ii) the rate constant, and (iii) the
half-life of A.
5.8
2
For the following autocatalytic reaction scheme for conversion of A
to C determine the rate of formation of C using the pseudo-steady-state
approximation:
A
k
1
−→
B,
B
+
C
k
2
−→
C
+
A.
5.9
3
Sulfur in the
+
4 oxidation state participates in a number of atmospheric
reactions.S(IV)representsthetotalconcentrationinthe
+
4oxidationstate:
[
HSO
3
]
. The second-order reaction of
S(IV) with a component A is given by A
+
S(IV)
→
products. (a) What
is the rate expression for the process? (b) Rewrite the above expression in
terms of the partial pressures of the species.
5.10
1
A first-order reaction is 30% complete in 45 min. What is the rate constant
in s
−
1
? How long will it take for the reaction to be 90% complete?
5.11
3
An important reaction in both atmospheric chemistry and wastewa-
ter treatment is the conversion of ozone to oxygen. In the gas phase
the reaction is 2O
3
(
g
)
3O
2
(
g
)
. This proceeds in steps as follows:
Step 1: O
3
+
M
k
a
S(IV)
]=[
SO
2
]+[
SO
2
H
2
O
]+[
O
2
+
O
+
M and Step 2: O
+
O
3
k
b
k
a
−→
2O
2
. M is a third
species.
(i) Using the steady-state approximation, obtain an expression for
the decomposition rate of ozone,
(ii) The following data were obtained for the thermal decomposition
of ozone in aqueous acidic solutions (Sehestad et al., 1991) at
304 K in the presence of [HClO
4
]=
0.01 M:
Initial Rate Constant (s
−1
)
[O
2
](
μ
M)
[O
3
](
μ
M)
1.3
×
10
−
4
10
200
7.0
×
10
−
5
400
200
4.7
×
10
−
5
1000
200
2.4
×
10
−
5
1000
95
8.0
×
10
−
5
1000
380
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