Calculate the concentration of the lactate ion in a solution that is 0.100 m in lactic acid (ch3ch(oh)cooh, pka = 3.86) and 0.080 m in hcl.

The concentration of the lactate is computed by:

Lactic acid ⇒ H+ + Lactate 
pKa = 3.86

Ka = 1.38 x 10^-4 would be equal to [H+] [lactate] / [lactic acid]

HCl ⇒ H+ + Cl- 
[H+] = 0.08 

Lactic acid = 0.10 M 

1.38 x10^-4 would be equal to 0.08 [Lactate] / 0.10 

Lactate = 0.10(1.38 x 10^-4/ 0.08 
Lactate = 1.73 x 10^-4