Question

Calculate the ph of a solution containing 0.75 m lactic acid and 0.25 m sodium lactate. recalculate after the addition of 0.05ml of hcl

Answer 1

pH= pKa+log[A-]/[HA]

pKa=-log(Ka)

-log(1.4/10^-4) (the Ka of lactic acid)

pKa=3.85

pH=3.85+log (0.25/.75)

pH=3.37

HCl is an acid, so the 0.05M HCl is added to the acid and subtracted from the base

pH= 3.85+ log(0.24/0.76)

pH=3.35 after addition of HCl