Let's save some typing time (and space) by using HL for lactic acid and NaL for sodium lactate. Then L^- will be the lactate ion.
millimols Lactic acid = mL x M = 74 mL x 1.0 M = 74 or 0.074 mols.
millimols sodium lactate = 25 mL x 1.0 M NaL = 25 or 0.025 mols.
(HL) = the acid = mols/L = 0.074/0.099 = ?
(NaL) = the base = mols/L = 0.025/0.099 = ?
Then plug into the Henderson-Hasslebalch equation of
pH = pKa + log [(base)/(acid)]
Post your work if you get stuck. You should get approximately 3.7 or so.
Calculate the PH of a buffer solution by mixing 74ml of 1.0M lactic acid and 25ml of 1.0 sodium lactate having a Pka of 3.86 lactic acid
2 answers
3.38