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CEE 680 |
Fall 2011 |
Homework #3
Determine
the complete solution composition of the following systems (all are added to 1
liter of pure water), based on the governing equations. Make one or more simplifying assumptions,
then solve the system of equations based on those assumptions, and check the
assumptions.
a. 5x10-3 moles HOCl
b. 5x10-3 moles NaCN
c. 5x10-8 moles HCl
d. 1x10-3 moles
HAc + 5x10-4 moles NaAc
Solve the following problems
(A. and B.) graphically. Later in
question #4, I will ask you to solve them exactly using MINEQL. Show the graphs and circle your solution
point. Then present the approximate
concentrations in a table.
A). Construct a log
C vs pH diagram for a 0.10 F phosphate (H3PO4, H2PO4-,
HPO4-2, PO4-3)
system. Using it, calculate the pH and
the concentration of all species in the following solutions:
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i) 0.10 F NaH2PO4 |
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ii) 0.10 F Na2HPO4 |
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iii) 0.10 F Na3PO4 |
B)
Construct similar log C vs pH diagrams for 0.10 F carbonate system (H2CO3,
HCO3-, CO3-2) and 0.20 F ammonia
system (NH4+, NH3), and use this to calculate
pH and composition of the following systems:
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i) 0.10 F NaHCO3 |
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ii) 0.10
F NaHCO3 +
0.20 F NH4Cl |
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iii) 0.10 F (NH4)2CO3 |
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iv) 0.10 F Na2CO3 |
A.) Calculate the composition and pH of the following
solutions[1]:
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i) 0.10 F NaCOOH + 0.40 F HCOOH |
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ii) 0.20 F NH3 + 0.50 F NH4Cl |
B.) A 3.16x10-3 F solution of uric acid has a pH of 3.2. What is the pH of an equimolar solution
(i.e., 3.16x10-3
F) of the Na+ salt of its conjugate base (Na-urate)?
Solve the problems from
question #2 (2A. and 2B.) exactly using MINEQL.
Present the MINEQL-based concentrations in a table. Compare your MINEQL results with the
approximate solutions you obtained from your graphs in problem 2 (note: when
solving problems with the carbonate system, you will have to send aqueous CO2
to the Type VI category just as you did for H+. When we work with open carbonate systems, you
won't have to do this.)
Due: Prob1: 3 Oct 11
Prob 2&3: 7 Oct 11
Prob 4: 12 Oct 11