Mass of Carbonates Needed to Raise Solution pH One Unit
An actual lab titration of a mildly acidic process water at a pH of 4.0 requires 0.9 grams/liter of Na2CO3 to raise the pH from 4.0 to 5.0; re-running the titration but this time using CaCO3 requires 2.2 grams/liter of CaCO3 to raise the process water pH from 4.0 to 5.0...essentially a 2.25X difference.

If we assume these titration values to be correct, how could we predict or determine the amount of each carbonate per liter of process water would be required to raise the solution pH to 7.0?

Would you use more or less carbonate per unit change in pH as you got solution pH closer and closer to neutral?