A groundwater has a pH = 8.4 and an alkalinity of 72 mg/L as CaCO3. The water is not initially equilibrated with the atmosphere.

(a) Calculate the concentration of H2CO3, HCO3 - , and CO3 2- in the water (in mole/L).

(b) Determine the alkalinity and pH of the water from part (a) after 3x10-4 M HCl, a strong acid that completely dissociates to H+ and Cl- when added to water, is added and allowed to equilibrate. Assume that the re-equilibration is rapid and total dissolved carbonate remains unchanged.