Dissolution of limestone and for the dissociation of bicarbonate ion to carbonate ion as follows:
CaCO3(s) −) = Ca2+ + CO2-3 K = 10−8.3
HCO−3 = H+ + CO2-3 K = 10−10.33
Attains equilibrium in a solution at pH 9.33 that contains 10−2 mol/L CaCO3(s) and 10−3.3 mol/L Ca2+.
(a) What is the HCO–3 concentration in the solution, assuming that activity coefficients for all species are 1.0?
(b) Would you expect the Ca2+ concentration to increase, decrease, or not change if the system changed in the following ways? For this part of the problem, do not assume that activity coefficients are 1.0. In each case, explain your reasoning briefly (1-2 sentences). For this part of the question, consider only the effect on the first reaction shown above.
(i) The concentration of CaCO3(s) is doubled.
(ii) The ionic strength of the solution increases, e.g., by addition of NaCl.
(iii) The pH is lowered slightly, without significantly altering the ionic strength.