The oxidation of pyrite can be represented by the reaction 4FES, pyrite + 150, + 14H20 4Fe(OH)3 ferrihydraite + 8SO3- + 16H* (a) Write the pe equation for this reaction at 250c. Remember that when calculating the free energy, the reaction is written so that the oxidised forms are on the left and reduced forms are on the right. (b) Calculate the pe when pH = 4, SO? = 10-3 mol L-1, the reaction is in equilibrium with atmospheric oxygen (Po, = 0.2 atm). Using the following thermodynamic %3D data. O2 HO SO,? Species AGK]/mol FeS2 -166.9 Fe(OH)3 -696.5 -237.1 -744.5