Environmental Engineering Reference
In-Depth Information
where it remained till the floodwaters were pumped out of the city two
weeks later. Work by Ashley et al. (2007) provided evidence that sedi-
ment deposited inside the homes had contaminant concentrations much
larger than that deposited outside. One such example was chlordane, a
common organochlorine pesticide, detected in the sediment inside the
homes. A concern arises about the potential for this species to volatilize
from the sediment and be found inside the vapor phase of the homes.
Additionally high concentrations of mold spores represents another sink
for these particles from the gas phase and returning residents and first
responders can inhale both the air inside the homes and the aerosolized
mold spores. Using a level I fugacity model determine the concentra-
tions of chlordane present in both the gas phase (
μ
g/m
3
)
and the aerosol
phase (mg/kg of mold) inside the home. For the aerosol phase the fugac-
ity capacity can be obtained from
Z
Q
=
10
(
log
K
+
log
f
om
11.91
)
Z
A
ρ
Q
×
10
9
. Note that log
K
oa
=
8.872,
f
om
=
0.60,
ρ
Q
=
5.31
×
10
−
18
kg/m
3
.
Chlordane properties are as follows: molecular weight
=
409.8,
K
aw
=
4.91 Pa m
3
/mol, and
K
sw
=
4265 L/kg. Sediment density is 2.5 g/cm
3
.
Volumes of air, aerosol, and sediment are 401. 6 m
3
, 6.7
×
10
−
8
m
3
, and
0.329 m
3
, respectively. (
Note
: This problem was provided by Nicholas
Ashley.)
3.18
2
The equilibrium constant for the dissociation reaction A
2
↔
2A is 6
×
10
−
12
atm at 600 K and 1
×
10
−
7
atm at 800 K. Calculate the standard
enthalpy change for this reaction assuming that the enthalpy is constant.
What is the entropy change at 600 K?
3.19
2
In a chemodynamics laboratory an experiment involving the activity of
sediment dwelling worms in a small aquarium was found to be seriously
affected for a few days. The problem was traced to bacterial growth aris-
ing from dirty glassware. Bacteria can survive even in boiling water at
atmospheric pressure. However, literature data suggested that they can be
effectively destroyed at 393 K. What pressure is required to boil water
at 393 K to clean the glassware? The heat of vaporization of water is
40.6 kJ/mol.
3.20
2
Obtain the enthalpy of vaporization of methanol. The vapor pressures at
different temperatures are given below.
−
oa
Temperature (
◦
C)
Vapor Pressure (mm Hg)
15
74.1
20
97.6
25
127.2
30
164.2
3.21
1
Can an assemblage of liquid droplets be in true equilibrium with its bulk
liquid? Explain your answer.
3.22
2
The formation of fog is accompanied by a simultaneous decrease in tem-
perature and an increase in relative humidity. If water in the atmosphere
is cooled rapidly to 298 K, a degree of super-saturation is reached when
water drops begin to nucleate. It has been observed that for this to hap-
pen the vapor pressure of water has to be at least 12.7 kPa. What will be
the radius of a water droplet formed under super-saturation? How many
Search WWH ::
Custom Search