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CEE
680 |
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Fall
2011 |
Water
Chemistry
Homework Set #7
1.
Nickel forms a series of complexes with aqueous ammonia. Draw a set of alpha curves (vs log[ NH3 ]) for the Nickel Ammonia system. Use the following stability constants
(determined from Smith & Martel; Vol.4, pg.40). Include also an n-bar curve.
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Log K1 = 2.72 |
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Log |
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Log K3 = 1.66 |
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Log K4 = 1.12 |
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Log K5 = 0.67 |
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Log K6 = -0.03 |
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2.
Determine the species composition of a solution containing 10 mM total nickel
and 30 mM total ammonia. Assume that the
solution is buffered at pH 10.3. Then
discuss the assumptions you might have made, and how changes in pH might affect
this system.
3.
Using MINEQL (and a graphics or spreadsheet package) prepare a Log
Concentration vs pH graph for the copper NTA problem solved in class. But this time assume a total concentration of
10-3 M for copper and 10-2.7 M for NTA. Show the same three species I plotted on my
graph, and use the same axis range. Are
there differences between your graph and mine?
Explain. Prepare a second graph,
but this time show other important soluble species and label them.
(Note: for this problem, I would refer
you to your earlier notes on MINEQL as well appropriate sections in the Version
4.5 MINEQL. Treat this as a pH titration
of a system containing Cu and NTA. Note
that since we’re imposing a pH, it will remain as a Type III species. MINEQL treats a pH variable run as a
“titration” where the “logK of pH” is allowed to vary over a fixed range
(0-14). Allow MINEQL to form all of the
species for which it has equilibrium constants.
Save the “Multi”, and “S2” files so that you can import them into your
favorite graphics or spreadsheet package.
I used a Lotus 123 format, which can be easily imported into Sigmaplot.)
Due: 18 Nov 11