Homework #4 � Using PHREEQ by 3UYFPmEM


									                         Problem Set #6 – Redox Reactions
                       Due Wednesday March 23, before class

(1) Surface seawater has a pH of 8.2 and the following redox couples present:
a) O2 at a pressure of 0.21 atm and water
b. N2 at a pressure of 0.76 atm and NO3- at a concentration of 4 x 10-5 m
c. CO2 at a pressure of 3 x 10-4 atm and CH4 at a pressure of 1.5 x 10-6 atm

Assuming T = 25º C, what pe does each couple define? Are they the same as each other?
What do you think are the reasons for the discrepancies?

(2) Construct a pe-pH diagram for the system Mn-O-H2O, considering Mn2+ and the
phases of MnO2 (birnessite), Mn2O3, Mn3O4, and Mn(OH)2 (pyrochroite).

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