Question

Write down as many correct, distinct, and relevant facts you can about:

150 mg of an organic compound Z is dissolved in 200 mL of water and extracted with an equal volume of hexane. The density of hexane is 0.66 g/mL. After allowing for mixing and equilibration, the non-aqueous phase is found to contain 100 mg of compound Z.   

6 statements are required

Answer 1

1. The concentration of Z in water = 150 mg/200 mL = 0.75 mg Z/mL water

2. The partition coefficient of Z between water and hexane (K) can be calculated as follows.

50 mg = {200/(200 + K*200)}¹ * 150 mg

i.e. K = 2

3. By using 2 times 100 mL extractions of hexane, the mass of Z in the aqueous phase (let's say 'x' mg) can be calculated as follows.

x = {200/(200 + 2*100)}² * 150 mg

i.e. x = 37.5 mg

4. By using 2 times 100 mL extractions of hexane, the mass of Z in the non-aqueous phase = 150 - 37.5 = 112.5 mg

5. By using 3 times 70 mL extractions of hexane, the mass of Z in the aqueous phase (let's say 'y' mg) can be calculated as follows.

y = {200/(200 + 3*70)}³ * 150 mg

i.e. x = 17.4 mg

6. By using 3 times 70 mL extractions of hexane, the mass of Z in the non-aqueous phase = 150 - 17.4 = 132.6 mg