when Ka =1.37 x 10^-4
∴Pka = - ㏒Ka
= -㏒ 1.37 x 10^-4
= 3.86
According to H- H equation:
when PH = PKA + ㏒[conjugate base / weak acid]
when the lactate is the conjugate base and lactic acid is the weak acid
∴ PH = Pka +㏒[lactate] / [lactic acid]
so, by substitution:
4.49 = 3.86 + ㏒[lactate]/[lactic acid]
∴[lactate]/[lactic acid] = 4.3
∴ [lactic acid] / [lactate] = 1/4.3
= 0.23
