You are given the following free energy data in kcal/mol for 25 degrees C and 1 bar total pressure. See below:
Species deltaGf Species deltaGf
Ca2+ -132.3 CaCo3 (calcite) -270.01
Mn2+ -54.5 MnCO3 (rhodocrosite) -195.2
CO2-3 -126.17
a) Assuming mangaoan calcite with a composition of Ca0.95Mn.05CO3 is an ideal solution, calculate its free energy of formation.
b) Write the dissolution reaction for the solid and calculate its solubility product.
c) The drinking water standard for dissolved Mn2+(aq) is .05 mg/L. Assuming dissolved Ca2+=10-3.00 M and CO2-3 = 10 -5.48 M compute Mn2+(aq) at equilibrium with this solid solution. Compare this result to Mn2+(aq) at saturation with respect to pure rhodocrosite. How do both of these concentrations compare to the drinking water standard?