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Although other solvents are available, dichloromethane
Chapter 14, Problem 101P(choose chapter or problem)
Problem 101P
Although other solvents are available, dichloromethane (CH2C12) is still often used to "decaffeinate" drinks because the solubility of caffeine in CH2Cl2 is 8.35 times that in water.
(a) A 100.0-mL sample of cola containing 10.0 mg of caffeine is extracted with 60.0 mL of CH2Cl2. What mass of caffeine remains in the aqueous phase? (b) A second identical cola sample is extracted with two successive 30.0-mL portions of CH2Cl2. What mass of caffeine remains in the aqueous phase after each extraction? (c) Which approach extracts more caffeine?
Questions & Answers
QUESTION:
Problem 101P
Although other solvents are available, dichloromethane (CH2C12) is still often used to "decaffeinate" drinks because the solubility of caffeine in CH2Cl2 is 8.35 times that in water.
(a) A 100.0-mL sample of cola containing 10.0 mg of caffeine is extracted with 60.0 mL of CH2Cl2. What mass of caffeine remains in the aqueous phase? (b) A second identical cola sample is extracted with two successive 30.0-mL portions of CH2Cl2. What mass of caffeine remains in the aqueous phase after each extraction? (c) Which approach extracts more caffeine?
ANSWER:
Solution 101P:
Step 1: (a)
Here, we are going to calculate the mass of caffeine remains in the aqueous phase.
Given that,
Volume of the sample =100 mL
The fraction of caffeine remaining in the aqueous phase
=
= 0.166
Therefore, the mass of caffeine remains in the aqueous phase = 0.166
= 1.66 mg