Question

a similar experiment to the one you have performed a student is measuring the equilibrium for an organic acid that is soluble in water and in cyclohexane, a nonpolar organic solvent. When shaken with the solution of water and cyclohexane, it distributes between the organic and aqueous phase. The two phases are separated and titrated with 0.12 M NaOH. Calculate the equilibrium constant for an acid where the titration of the aqueous phase requires 6.1 mL of the base and the organic phase requires 5.84 mL of the base.

Answer 1

we can solve this question using the partition law, which states

A solute distributes itself between two immiscible liquids so that the ratio of its concentration in each solvent is constant at constant temperature

Partition coefficient / distribution coefficient, K (a constant)

= (Concentration of X in solvent A / Concentration of X in solvent B)

now,

concentration in aqueous phase = 0.12 X 6.1 X10^-3

concentration in organic phase = 0.12 X5.84 X10^-3

therefore value of k = 1.044