For this question, you can assume that activities equal concentrations, i.e. that g = 1 for all species. Values of K:

20C 10C

K_CO2 (Henry's Law constant) 10^-1.41 10^-1.27 K_H,CO2 = [H₂CO₃]/P_CO2

K_sp,calcite 10^-8.45 10^-8.41 K_sp,calcite = [Ca²⁺].[CO₃^2-]

K₁(H₂CO₃) 10^-6.38 10^-6.46 K₁ = [H⁺].[HCO₃^-]/[H₂CO₃]

K₂(H₂CO₃) 10^-10.38 10^-10.49 K₂ = [H⁺].[CO₃^2-]/[HCO₃^-]

(a) What are the pH and calcium concentration (in moles/L) of a water in equilibrium with calcite at a P_CO2 of 10^-2.0 atm at 20C?

(b) What are the pH and calcium concentration (in moles/L) of a water in equilibrium with calcite at a P_CO2 of 10^-2.0 atm at 10C?