You want to decaffeinate your coffee by extracting the caffeine outwith dichloromethane. It's too late to extract the caffeinefrom the coffee beans because you've already brewed yourself a 200mL cup of coffee. Your particular brand of coffee contains100 mg of caffeine in that 200mL cup. The partitioncoefficient of caffeine in dichloromethane/water is 9.0. How much caffeine would still be in your 200 mL if you did:
A. One extraction using 200 mL o fdichloro methane
B. Two extractions using 100 mL of dichloro methane each.

Solution :

The partition coefficient

   = 9.0

A). 1 x 200 mL extraction

Let m be the mass of caffeine in water

Mass of caffeine in = 100 - m

∴

     = 10

Therefore, the mass remaining in the coffee is m = 10 mg

B). 2 x 100 mL extraction

First extraction :

Let be the mass of the caffeine in water.

Mass of caffeine in = 100 - m

∴

     = 18.18

Mass remaining in the coffee after the 1st extraction = 18.18 mg

Second extraction:

Let be the mass of the caffeine in water.

Mass of caffeine in = 18.18 -

∴

     = 3.3

Mass remaining in the coffee after the 1st extraction = 3.3 mg

quartz

explanation: