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Author Question: A student started with 100 mg of an unknown solid and recrystallized this material from water. The ... (Read 36 times)

Destiiny22

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on: Aug 23, 2018
A student started with 100 mg of an unknown solid and recrystallized this material from water. The weight of the crystals they isolated was 27 mg. Explain why the student might have obtained this result and what the student can do to try to correct the problem.

Question 2

A student started with 100 mg of an unknown solid and recrystallized it from water. The weight of the crystals isolated was 120 mg and the melting point range was very broad and lower than the literature value. Explain the problem that the student encountered and how the student can solve it.


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14vl19

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Reply #1 on: Aug 23, 2018
Answer to Question 1

The hot solution was probably not saturated and therefore recrystallization would be inefficient. They should attempt to obtain a second crop of crystals by concentrating the mother liquors.

Answer to Question 2

The crystals are most likely wet with the solvent used for recrystallization. The student should let the crystals dry until the weight is constant and then recheck the melting point.


Destiiny22

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Reply 2 on: Aug 23, 2018
Great answer, keep it coming :)

juliaf

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Reply 3 on: Yesterday
Excellent

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