You want to decaffeinate your coffee by extracting the caffeine outwith dichloro

Question

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 ofdichloromethane B. Two extractions using 100 mL ofdichloromethan each. Please show all steps! Thank you!

Explanation / Answer

Dear friend

                                                                       [g/100 mL] in organic phase

                        Partition coefficient (K) =         ----------------------------------------------------

                                                                       [g/100 mL] in aqueous phase

The partition coefficient of caffeine in dichloromethane/water is 9.0. it means for every 100 mL 90 mg caffeine goes into dichloromethane and 10 mg goes into water.

A. One extraction using 200 mL of dichloromethane ------   10 mg remains because 90 mg goes into 200 mL dichloromethane

B. Two extractions using 100 mL of dichloromethan each ------    nothing remains because first 100 mL takes 90 mg then next 100 mL takes 10 mg into dichloromethane.

Thank you.

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