What mass of solid sodium formate (of MW 68.01) should be added to 130 mL of 0.63 mol/L
formic acid (HCOOH) to make a buffer solution
have a pH of 3.68? Ka = 0.00018 for
HCOOH.
Answer in units of g
I tried converting pH to H+ and using the Henderson-Hasselbalch equation and got 6.465232859g which is apparently wrong. A full explanation would be welcome! The HH equation is
pH = pKa + log (base)/(acid)
Calculate the pKa for Ka listed.
Plug the pKa and pH and mol acid into the HH equation. Solve for (base) = Naformate mols. Convert Naformate mols to grams and you have it. I’ve gone through a rough ballpark and think grams of Naformate = about 5g.