Question

The question asks, "Butanoic acid has a partition coeff of 3.0 when distributed b/t water and benzene. Find the formal concentration of butanoic acid in each phase when 100 mL of 0.10 M aqueous butanoic acid is extracted with 25 mL of benzene at pH 10.00."

I know that the first step is to find D, where D = K(Ka)/[(Ka+[H+)].

So I calculated:
D = 3.0(1.52x10^-5)/[(1.52x10^-5+10^-10)].

The answer should have been D = 1.97 x 10^-5, but I didn't get this.

Please help!

Answer 1

If the question is worded correctly, then K_{d water/benzene} = 3.0

Answer 2

However, the distribution coefficient USUALLY is listed as organic/water.

Answer 3

So how do I correct my mistake?