Ka1 = 4.5E-7 and Ka2 = 4.7E-11 for the carbonate system. Ksp is 5.0E-9 and Kw =1.0E-14. A town’s groundwater has [Ca2+] = 37 mg/L, alkalinity of 1.36E-3eq/L and pH of 8. This is to be mixed with surface water with [Ca2+] = 4mg/L, alkalinity of 8.0E-4 eq/L and pH of 9.5. Assume closed system (no exchange with atmospheric carbon dioxide) and that the alkalinity is all due to bicarbonate, carbonate, hydroxide and proton only.
a)Calculate the Ct (or TIC) of the groundwater and the surface water.
b)If the groundwater and surface water are mixed at a 1:1 ratio, you can just take the average of the alkalinity and Ct and calcium, what will be the pH of the mixture?
c)Will the mixture be prone to precipitation of CaCO3(s)? Are there other considerations we should take before answering this question?
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