October 17, 2021, 10:06:22 PM
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Topic: Organic chemistry solubility problem  (Read 232 times)

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Offline K1Ko

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Organic chemistry solubility problem
« on: October 06, 2021, 03:47:19 PM »
Hello everyone! I have this problem which i haven’t been able to solve, i would really appreciate it if anyone could help me solve it. Thank you in advance :)
A solid (A) is soluble in water to the extent of 1 g per 100 ml of water at room
temperature and 10 g per 100 ml of water at the boiling point. How would you
obtain pure A from a mixture of 10 g of A, 1 g of impurity B (B has the same
solubility in water as A) and 0.1 g of impurity C (C is insoluble in water)?
How many grams of pure A could be obtained after one recrystallization from
water?
How much pure A could be obtained after one recrystallization from a mixture of 10
g of A, 9 g of B and 8g of C?

Offline Borek

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Re: Organic chemistry solubility problem
« Reply #1 on: October 06, 2021, 03:58:23 PM »
Please read the forum rules. You have to show your attempts at answering the question/solving the problem to receive help, it is a forum policy.

However, if

(B has the same solubility in water as A)

there is no way to separate them with water.
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Offline mjc123

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Re: Organic chemistry solubility problem
« Reply #2 on: October 07, 2021, 06:05:08 AM »
You can if you want pure A, but are not concerned to recover all the A present in the mixture. This appears to be what the question is asking.

Offline Borek

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Re: Organic chemistry solubility problem
« Reply #3 on: October 07, 2021, 01:53:10 PM »
You can if you want pure A, but are not concerned to recover all the A present in the mixture. This appears to be what the question is asking.

I am not sure how. "B has the same solubility as A" sounds to me like not only it dissolves in the same amount, but also its solubility changes with temperature in exactly the same way. If so, you will always get a mixture.

Can be you are right about the intent and this is just a problem with poor wording, still.
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Offline mjc123

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Re: Organic chemistry solubility problem
« Reply #4 on: October 07, 2021, 05:15:16 PM »
You could put the 11g mixture in 100 ml cold water; all the B and 1g of A would dissolve, leaving 9g of solid A.

Offline Borek

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Re: Organic chemistry solubility problem
« Reply #5 on: October 08, 2021, 02:51:45 AM »
Good point, I concentrated on the solution.
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