Hw4 Assignment
ADVERTISEMENT
1
2CEE 543 Aut 2012 HW#4
−2.7
−3
1. A wastewater is simulated as an ideal solution containing 10
M NaHCO
and 10
M
3
NH
Cl.
4
a. Prepare a log c - pH diagram for the system and use it to determine the pH of the solution.
Assume ideal behavior of the solutes.
b. The utility hopes to remove nitrogen from the solution by volatilizing NH
gas. To prepare
3
+
for that step, 148 mg/L Ca(OH)
(lime) will be added to raise the pH and convert
NH
to
2
4
the NH
(aq) form. Calculate the pH after lime addition. (Assume that no CaCO
3
3
precipitation or ammonia loss takes place during lime addition; i.e., all species remain in
solution.)
c. If CaCO
precipitation did occur during lime addition would it raise, lower, or not change
3
the pH of the solution? (Hint: Consider what species are removed from solution by this
reaction, and what the response would be of the species that remain.)
d. Would removal of NH
(aq) by volatilization raise, lower, or not change the pH of the
3
solution? Explain your reasoning briefly.
2. Hypobromous acid, HOBr, is an analog of HOCl and participates in many similar reactions,
including the reaction with natural organic matter to form halogenated disinfection
byproducts. Although HOBr is never added to water as a disinfectant, it can form if ozone
−
(O
) is used as a disinfectant in water that contains bromide (Br
) ions. Neither HOBr nor its
3
−
−
conjugate base, OBr
, is included in the default Visual Minteq database. Add OBr
species to
the database for components and HOBr to the database for species, and determine the
composition of an ideal solution containing 0.01 M each of NaOBr and NaOCl. Assign values
−
of a = 3 and b = 0 for the Debye-Huckel parameters for OBr
in Visual Minteq. [Values for
these parameters must be input in the database, but they have no effect on the calculations
when the Davies equation (the default option) is used to determine activity coefficients.]
Identify which one of the two bases has the greatest effect on solution pH, and explain your
reasoning. pK
for HOBr is 8.63.
a
−2.7
3. A log c - pH diagram for an acid/base system containing 10
M TOTA is shown below. The
fully protonated form of the acid is H
A. However, the curves are shown for only three
4
species, because one of the potential H
A species is so unstable that its concentration in this
n
−8
system is always less than 10
M. The s values indicate the approximate slopes of the curves
in the given region, and the pH values indicate the intersection points of the various curves.
A ↔ HA + 2 H
+
What is the equilibrium constant for the reaction H
? What is the value of K
3
b
for a reaction in which HA is the acid?
ADVERTISEMENT
0 votes
Related Articles
Related forms
Related Categories
Parent category: Education