Easy question for my pre-lab in Organic Chemistry?

Question

Hi guys. I'm just having difficulty with this one problem. There were two, I answered the first one which was:

1. Calculate how much 95% ethyl alcohol will be required to dissolve 0.3g of sulfanilamide at 78 ' C.

I got 300 mg sulfanilamide ( 1ml / 210mg SAmide) = 1.42867143ml.

Now it is asking:

2. Using the volume of solvent calculated in Step 1, calculate how much sulfanilamide will remain dissolved in the mother liquor after the mixture is cooled to 0 ' C.

I know the solubility of sulfanilamide at 0 ' C is 14 mg/ml but I don't know where to go after this. Please help me understand this problem! Any help will be much appreciated. We are doing a Semimicroscale Crystallization lab using Erlenmeyer Flasks and a Hirsch Funnel. Thank you all in advance!

Answer 1

I do not know previously the solubility of sulfanilamide in 95% ethyl alcohol. Let us accept the solubility you quoted here.
300/210 = 1.428571428.. ≈ 1.43 (ml)
at 0C, the amount of sulfanilamide remains in the solution is:
14*(300/210) = 20 (mg), since you only have 1.43ml solution.
The volume of the solution will change a little by cooling from 78C to 0C. You may also consider this volume change if you have data.

Answer 2

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RE:
Easy question for my pre-lab in Organic Chemistry?
Hi guys. I'm just having difficulty with this one problem. There were two, I answered the first one which was:

1. Calculate how much 95% ethyl alcohol will be required to dissolve 0.3g of sulfanilamide at 78 ' C.

I got 300 mg sulfanilamide ( 1ml / 210mg SAmide) = 1.42867143ml....

Answer 3

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The key to organic chemistry is to not memorize anything! There is simply too much. People who do well at organic chemistry (I am an organic chemist) are those who don't try and memorize the material. Rather, if you understand the basic concepts of nucleophilicity, electrophilicity, leaving groups, etc. you can determine everything from first principle, and then the material will then never be forgotten. Too many people attempt to learn organic chemistry by memorizing the material, and in the end they learn nothing, have a miserable time, and completely miss the beauty and simplicity of organic chemistry.

Answer 4

Ok, psychiatrydude, Taking orgo over a month is a bit of an undertaking, but very doable. The key to the class is simply memorizing reactions. Theoretically, a business or sociology major could get an A in the class as long as one is willing to put in the time. The best advice I can give is make notecards and carry them around whereever you went. When I took the class, everytime I took the subway, elevator, waited in a Dr.'s office, etc, I had them out. As long as you can put in the time, you can do it. The lab will be difficult as many of the reactions are complicated, but once again, very doable.

Answer 5

Sulfanilamide Solubility