posted by Lauren .
Lactic acid, C3H6O3, is found in sour milk. A solution containing 1.00g NaC3H5O3 in 100.0mL of 0.0500M C3H6O3 has a pH= 4.11.
Calculate the Ka of lactic acid
Let lactic acid = HL
The salt, then, is NaL.
I would use the Henderson-Hasselbalch equation but it can be done without that.
Substitute 4.11 for pH.
(base) in the HH equation = 1g/molar mass NaL.
(acid) in the HH equation = 0.05
Solve for pKa and convert to Ka.