Bethel Changani, Danny Chipampe and Chinyanta Ndhlovu (R = 8.314 J K-1 mol, 1 Faraday = 96500 coulombs mol-1 ,ln X = 2.303 log10X, 273K = 0oC) Please use graph paper. Ignoring dissolved species, draw an Eh - pH diagram to represent the equilibrium among magnetite, siderite, metallic iron and water, at a partial pressure of CO2 of 10-2 , 1 atmosphere total pressure and 25oC. Indicate metastable equilibria (if any) by a dashed line. From the diagram answer Yes or No to the following questions:

(i) Can iron and magnetite co-exist?

(ii) Can water and siderite co-exist?

(iii) Can oxygen and siderite co-exist?

(iv) Can hydrogen and magnetite co-exist?

Species Go f (kJ mol-1 )

Iron 0

Magnetite (s) - 1015

Siderite (s) - 667

Water (l) - 237

CO2 (g) - 394

H2 0

H+ 0