Solid sodium carbonate is slowly added to 50.0 mL of a 0.0310 M calcium acetate solution. The concentration of carbonate ion required to just initiate precipitation is

Answer 1

Ksp = (Ca^2+)(CO3^2-)
You know Ksp, you know (Ca^2+---it's 0.0310M), solve for (CO3^2-). The 50 mL is not used.