[wassimtaleb]

Do you know how to use the Henderson-Hasselbach equation or other method  to compute how much salt (mg) you should add to a solution to get a desired pH?
Example, calculate how much NaHCO3 salt you must add to a 3.5% NaCl CO2 saturated solution of pH (4) to higher it to a pH of 7?
Cheers

[Borek]

First step would be to find the concentration of carbonic acid (assuming it is equal to the concentration of CO₂), then finding necessary concentration of HCO₃^- is rather trivial. You may want to use Ka values corrected for the ionic strength of the solution.

[wassimtaleb]

Thx,
so do you just use the below formula with the H₂CO₃/NaHCO₃ system having a pKa of 6.37? Or you should also take into account the PKa2 of the NaHCO₃/Na₂CO₃ (10.25) and how will the formula change?

pH=PKa+log[HCO₃^-]/[H₂CO₃]

[Borek]

You can safely ignore pKa2.