Calculate the activity of Fe in coexisting magnetite and hematite at 700°C, 1 atm (the relevant equation is shown in §14.7). Calculate  for the other iron-mineral pairs FeO – Fe3O4, FeO – Fe at the same T, P. This should be sufficient to demonstrate the use of   a redox indicator.

Of course, our new indicator is limited to systems containing iron. But then, f is limited to systems containing oxygen (though not necessarily ). True? On the other hand,  can also be used as a sulfidation indicator. Calculate  in coexisting pyrite and pyrrhotite in which  is 0.9, at 500 K, 1 bar

1.Calculate Ksp for anhydrite at 25°C (verifying the value given in the text), and at 300°C.   2.Calculate the dissociation constant for NaCl(aq) at 25°C, 1 bar. Calculate this constant at 500°C, 1 and 2 kbar, obtaining the necessary values of e and Y from Tanger and Helgeson, (1988). A graph of –KNacl versus T  is shown by Sverjensky (1987)

These problems can be done with a hand calculator, but it can be very frustrating. They are best done by writing small computer programs, partly because of the complexity and partly because some of the results are sensitive to round-off errors. If you have access to the program SUPCRT92, or some other program, you can do the HKF problems quite easily, but you will not […]

Calculate for anhydrite, Ca2+, and S. at 25 and 300°C, using equation (17.77) for the ions and (7.25) for anhydrite. The Born parameter YPr,Tr is -5.81 x 10-5 at 25°C, 1 bar, and the dielectric constant e is 19.99 at300°Cand78.46at25°C.

1. Fit these GEX values to equation (15.42). This is best done with a multiple linear regression program, using  and  as the independent variables. Comparing the fit coefficients with (15.42), calculate W and WG for CO2. Answers in Problem 3 at the end of Chapter 12.   2. . Show that WGC is the same as  as discussed in   1. Fit these GEX values to equation (15.42). […]

1.If for Pb2+ (aq) is -5832 cal mol-1, at what Eh is metallic lead in equilibrium  with    m Pb2+(aq)?   2.Water draining from abandoned coal mines causes considerable environmental damage because of its iron content and acidity. In an attempt to understand the chemistry of these waters, the following measurements were made in water in the Loree #2 shaft near Wilkes-Barre, PA. (Barnes et al., […]