Chemistry · May / June 2022 · Paper 62 · Question 4
0620
As printed in the paper
The question as text
The diagram shows some coffee beans. Caffeine occurs naturally in coffee beans. Caffeine is a white crystalline solid. It is very soluble in hot water but much less soluble in cold water. Plan an investigation to obtain a pure crystalline sample of caffeine from coffee beans. Assume that all other soluble substances in coffee beans are very soluble in both hot and cold water. You are provided with coffee beans and common laboratory apparatus. [6]
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Show the answer and mark scheme
any 6 from:
grind / crush / powder coffee beans
using pestle / mortar
add water and stir / mix
heat / hot (water) (to dissolve)
filter
leave (filtrate) to cool or leave to form crystals
wash / rinse (crystals / residue / caffeine)
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