Environmental Engineering Reference
In-Depth Information
3.55
2
A solution of benzene and toluene behaves ideally at 25
◦
C. The pure com-
ponent vapor pressure of benzene and toluene are respectively 12 kPa and
3.8 kPa at 298 K. Consider a spill of the mixture in a poorly ventilated
laboratory. What is the gas-phase mole fraction of benzene in the room?
Use Raoult's law. The mixture is 60% by weight of benzene.
3.56
2
Five grams of soil contaminated with 1,4-dichlorobenzene from a local
Superfund site were placed in contact with 40 mL of clean distilled water
in a closed vessel for 24 h at 298 K. The solution was stirred and after
72 h the soil was separated by centrifugation at 12,000 rpm. The aqueous
concentration was determined to be 35
μ
g/L. If the partition constant was
estimated to be 13 P/kg, what is the original contaminant loading on the
soil?
3.57
2
Estimate the activity coefficient of oxygen in the following solutions at
298 K: (a) 0.01 M NaCl; (b) seawater (see problem 3.69 for composition);
and (c) wastewater containing 0.001 M Na
2
SO
4
and 0.001 M CaSO
4
. Use
the McDevit-Long equation from the text.
ϕ =
0.0025. Oxygen solubility
in pure water is 8.4 mg/P at 298 K and 1 atm total pressure.
3.58
2
The Henry's constant for methyl mercury at 0
◦
C is 0.15 and at 25
◦
Cis
0.31. Estimate the enthalpy of dissolution of gaseous methyl mercury in
water.
3.59
3
In pure water the solubility of benzo-[
a
]-pyrene varies as follows:
t
(
◦
C)
C
i
(nmol/L
)
8.0
2.64
12.4
3.00
16.7
3.74
20.9
4.61
25.0
6.09
The melting point of the compound is 179
◦
C. Calculate the excess entropy
of solution at 298 K.
3.60
2
Siloxanes are used in the manufacture of a number of household and
industrial products for everyday use. It is therefore of importance to know
its distribution in the environment. Consider octamethyl cyclotetrasilox-
ane (D4) whose properties are given below:
K
aw
=
0.50, log
K
ow
=
5.09, log
K
sw
=
2.87. For an evaluative environment of total volume
10
9
m
3
which is 50% air, 40% water, and 10% sediment, which com-
partment will have the highest fraction of D4? Use the fugacity level I
model.
3.61
2
Atmospheric reactions in hydrometeors (rain, fog, mist, and dew) produce
aldehydesandketones.Considertheconversionofpyruvicacidtoacetalde-
hyde in fog droplets. The reaction is CH
3
-C(O)-COOH
(
g
)
→
CH
3
CHO
CO
2
(g). (a) Obtain the standard free energy change for the reaction
at 298 K. (b) What is the equilibrium constant for the reaction at 298 K?
3.62
2
It is known that when deep sea divers come up rapidly from their dives,
they get what is called “bends.” This is due to the formation of bubbles
on nitrogen in their blood serum (approximated as water). If the Henry's
constantfornitrogenis8.6
×
10
3
atm,whatistheconcentrationofnitrogen
in the blood serum of a diver who came up from 200 ft below sea level?
(
g
)
+
Search WWH ::
Custom Search