Question

Suppose caffeine has a partition coefficient of 2.5 between dichloromethane and water (2.5/1 = dichloromethane/water). You are given a solution of 10 grams of caffeine dissolved in 100 mL water. You extract your caffeine solution 1 x 100 mL dichloromethane, and evaporate your dichloromethane layer. How much caffeine would you expect to isolate?A) 8.0 grams B) 7.5 grams C) 7.1 grams D) 6.5 grams E) 2.9 grams

Answer 1

Answer: Option (C) is the correct answer.

Explanation:

It is given that partition coefficient between dichloromethane and water is 2.5. Let us assume that "x" grams of caffeine is present in 100 ml.

Hence, find the value of x as follows.

          2.5 = $\frac{\frac{x}{100}}{\frac{(10 - x)}{100}}$

            x = 25 - 2.5x

           x = 7.14

or,        x = 7.1

Therefore, we can conclude that caffeine extracted is 7.1 grams.