In a “precipitation titration,” the concentration of an ion is measured as it forms a precipitate. The concentration of CO₃^2– ions in a sample of volume 25.0 mL was determined by titrating with 0.110 m AgNO₃(aq). Before the stoichiometric point, the Ag⁺ ions react immediately with the CO₃ ^2– ions, but after the stoichiometric point the concentration of Ag⁺ ion increases rapidly.

(a) The stoichiometric point is reached after the addition of 36.2 mL of the AgNO₃(aq). What is the concentration of CO^{+ 2–} ions in the sample?

(b) The concentration of Ag⁺ ions is followed by using a special electrode and measuring pAg (that is, –log [Ag⁺]). Sketch the plot of pAg against volume of AgNO₃(aq) and determine the value of pAg at the stoichiometric point.