A solution containing a mixture of lactic acid and lactate was found to have a pH of 3.51. Calculate the ratio of the lactate concentration to the lactic acid concentration in this solution.

0.4467

Explanation:

The solution of the lactic acid and lactate acts as a buffer.

Considering the Henderson - Hasselbalch equation for the calculation of the pH of the buffer solution as:

pH=pKa+log[Conjugate base]/[acid]

Where Ka is the dissociation constant of the lactic acid.

So, pKa of the lactic acid = 3.86

pH = 3.51

So,

3.51 = 3.86 + log[Lactate]/[Lactic acid]

log[Lactate]/[Lactic acid] = - 0.35

Or,

[Lactate]/[Lactic acid] = 0.4467