You perform an alkalinity test on a water sample with an initial pH of 9.75. The alkalinity is 12.1 mg/L as CaCO3. 

(a) Calculate the CT value.  1.54×10-4 M 

(b) Determine whether there is any potential to precipitate CaCO3 in the pipes given a calcium  concentration of 15 mg/L. Justify. Calculations show that it exceeds the Ksp, so yes there is a potential.

(c) For the same calcium concentration and CT, determine the potential to precipitate CaCO3 if the pH were to be lowered to 7. No, but why? Show calculations.