Question

Assume that the solubility of caffeine in water is 4.0 g/100 mL and in methylene chloride it is 16.0 g/100 mL at 25°C. What is KD for this system?

Answer 1

K_D = Partition coefficient

KD = [Caffeine]_H2O / [Caffeine]_CH2Cl2

= (4.0 g/100 mL) / (16.0 g/100 mL)

= 4 / 16

= 0.25

The distribution coefficient of caffeine between water and methylene chloride is 0.25

Again,

KD = [Caffeine]_CH2Cl2 / [Caffeine]_H2O

= (16.0 g/100 mL) / (4.0 g/100 mL)

= 16 / 4

= 40.25

The distribution coefficient of caffeine between methylene chloride and water is 4.