EXAM IV
CHM 336
Due 12-17 by 3:00pm.
This is not an open book exam, and you must complete this exam on your
own!
Your first job after good old YCP is with Ralph Nader's Public Interest
Research Group as the lead analytical chemist.
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For 35 points, your first problem is with the levels of EDTA in
Mountain Dew. Jane Doe of Dullsville, Alabama died of iron deficiency (severe
anemia). The following are necessary for your analysis;
a) Calculate the conditional
formation constant for the Fe3+-EDTA complex.(you will
need
to use your fractional composition graph to find alphaY4- )
b) Normal iron levels in
the blood are 1µg/mL
c) Normal absorption of Fe3+
from daily intake is 0.01mg.
d) Jane Doe was known to
drink 2L of Mountain Dew each day.
Could Mountain Dew have caused
Jane Doe's death?
Please be sure to support
your answer with calculations and graphs!
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Next we have an environmental issue for 25 points. The accepted
method for magnesium analysis is EDTA titration of water samples. In a
well known stream study there is a problem with interference due to possible
high levels of Cd2+ and Fe2+.
a. Start by looking at titrating
with EDTA, the controversy is over the level of
interference when you are
titrating Mg2+.
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Use equation 13-11 on page 327 to compute the titration of 100mL 0.025M
Mg2+, Cd2+, and Fe2+ with 0.005M EDTA
at a fixed pH=10.
b. Now solve the issue
of the change in titration with a change in pH by showing the effect
of pH on the Mg2+ titration at pH= 5, 7, 8, 9, 12.
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The lightweight rechargeable battery issue is your next challenge.
Zn(s) l ZnCl2(aq) ll Cl-(aq) l Cl2(l)
l C(s)
* l refers to a boundary
For 20 points
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Draw the cell that is described above.
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Write an oxidation for the left half and a reduction for the right half.
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Now calculate the standard cell potential.
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Finally, if the battery delivers a constant current of 3.00 x 103A
for 45minutes, how many kilograms of Cl2 will be consumed?
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For 20 points, describe how you might approach an unknown sample
using all of the techniques that you have been exposed to in quantitative
analysis. You may define the analytes and properties any way that is reasonable,
just remember that you are trying to incorporate all of your experience
(including lab ) into this scenario. You must include a brief description
and diagram of the UV/VIS and AA for full credit.