Question

What is the ratio of lactic acid (Ka = 1.37x10-4) to lactate in a solution with pH =4.36?

Answer 1

$pH=pka +Log$ [ (lactate ion) / (lactic acid ) ]

pH = 4.36 , $pka$ = -log $1.37 ×$ 10^-4

=3.86

4.36=3.86 + Log [ (lactate ion) / ( lactate acid ) ]

Log [ lactic ion / lactic acid ] =4.36 -3.86 = 0.50

[ lactic ion / lactic acid ] = 10^0.50 = 1.1220 / 1

Ratio of lactic acid to lactate Ion

= 1 / 1.1220

=1.1220 : 1