[itex]Ca^2^+[/itex] comes from [itex]Ca(OH)_2[/itex], which is a weak base due to it's low solubility. [itex]CO_3^2^-[/itex] comes from the weak acid [itex]HCO_3^-[/itex]. To compare the two we compare:

1) [itex]Ca^2^+ + H_2O --> Ca(OH)_2 + H_3O^+[/itex]

and

2) [itex]CO_3^2^- + H_2O --> HCO_3^- + OH^-[/itex]

We want to compare the K values. It is clear that equation 2 will have a significantly larger K value and the solution will be basic, but where can a person find a K value for something like equation 1?

Are there charts for the Ka of metal ions?

What order of magnitude is it? I imagine Ka for 1 is <<< Kw