Homework #2
1. How
many grams of anhydrous Sodium Sulfate (Na2SO4) must be
added to a liter of water so that the ionic strength equals 0.01M?
2. The
pesticide, parathion, undergoes photolytic degradation (destruction by
absorption of energy from the sun’s rays) in natural waters. This is a first order process with a rate
constant of 8x10-7s-1.
a.
What is the half-life for parathion based on
this degradation process?
b.
How long will it take for 90% of the parathion
to degrade?
c.
How long will it take for 99% of the parathion
to degrade?
3. Hypochlorous
acid (HOCl) reacts with phenol (C6H5OH) to produce a wide
range of products including highly offensive chlorophenols. The rate of this reaction is second order,
overall (first order in each reactant). The rate constant is 2x103 M-1s-1. In this problem you have 1.2 ppb of phenol in
water, and to this you add 0.1 mM hypochlorous acid.
a.
How long will it take to destroy 50% of the
phenol?
b.
How long will it take to destroy 99.99% of the
phenol?
4. Calculate the ThOD of the following wastewaters
a.
45 mg/L of methanol
b.
10 mg/L of glucose
c.
45 mg/L of methanol with 10 mg/L glucose
d.
10-4 M acetic acid
e.
5 mg/L of trichloroethane
5. Nitrogen
occurs at a variety of oxidation states in water environments. Balance the
following oxidation-reduction reaction which is important in wastewater
treatment:
NH3 + O2
→ NO3- + H2O
Show all steps.
Assigned: 24 Sept 10
Due: 1 Oct 10
Answer Page
Fill in the boxes with the correct answer.
You will only get credit for a problem if you (1) fill in
the box with the correct answer, (2) your answer is legible, and (3) you
include attach page(s) with calculations backing up your answer, when requested
for the problem.
Problem #
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2
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a
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hours
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b
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hours
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c
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hours
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4
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a
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mg-O2/L
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b
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mg-O2/L
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c
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mg-O2/L
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d
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mg-O2/L
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e
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mg-O2/L
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5
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1NH3 +
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O2
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=
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NO3- +
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H+ +
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H2O
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