Given a PH of buffer solution is 4.23 made from 0.35 formic acid. Calculate the concentration of formate.The constant dissociation for formic acid is 3.75

Answer 1

Use the Henderson-Hasselbalch equation.
4.23 = 3.75 + log(base)/(0.35) and solve for (base) = (formate) but before you do any of that you need to determine if that 0.235 is M, m, g/mL or just what. You should be M. Also, I assume that 3.75 is the pKa but you say in the post it is Ka.