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Offline avjazz78

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intro and question
« on: March 30, 2007, 01:48:05 PM »
Hi to all, this is my first post.

I'm am a junior in high school and this year am taking AP Chemistry, a first year college level course. It is without a doubt the hardest of all the AP science classes that I have ever taken but it has struck up somewhere within me a grave curiosity in chemistry and doing home experimenting, amateur scientist.

Just for fun, the first experiment that I wanted to try was supersaturation. We never did it as a lab in class (we don't do many labs) and if you can get it to work right it is a really cool experiment. My first round draft pick is Sodium Acetate which seems to be the choice all over. I chose, mostly because I have no idea where to get Sodium Acetate salt in the California desert and know of only one other more difficult way to make it, to react Acetic acid (Distilled white vinegar) and Sodium Bicarbonate (Baking soda.) Sounds simple enough, I add the Bicarbonate to the acid and watch it give off its beautiful odorless CO2, leaving me an aqueous soln. of Sodium Acetate. However, when I boil off the water, it leaves me with these weird brown colored crystals, doesn't look at all like Sodium Acetate.

Anyone have any idea on how to get any better results or any way to purify the crystals that result?
Thank you in advance
PK
KD7WNJ

Offline Sam (NG)

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Re: intro and question
« Reply #1 on: March 30, 2007, 05:50:17 PM »
It will be impurities introduced through using the vinegar from white wine.  If you want white crystals you need to use pure acetic acid.  In order to purify crystals you could try a recrystallisation, or redissolving the sodium acetate in water and doing a solvent solvent extraction?
« Last Edit: March 30, 2007, 06:27:45 PM by Sam (UoN) »

Offline Ψ×Ψ

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Re: intro and question
« Reply #2 on: March 30, 2007, 11:12:04 PM »
If you used tap water, the brown crud is probably not from the vinegar.   :o 
It's an interesting little demonstration.  My teacher used one of those little heat pads.  Should be able to buy them at the store (maybe large grocery chains would carry them?) or on Ebay.  Maybe not as interesting as recrystallizing your own, but it's easier and you still get to see the concept in action.
Best of luck in AP chem.  I hated it at first, but by the end of the year I was set on a chemistry major. 

Offline avjazz78

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Re: intro and question
« Reply #3 on: March 31, 2007, 01:50:33 AM »
I know that feeling, I now somehow love and hate chemistry all at the same time. The class has certainly turned me into an amateur chemist.

The brown comes from the the boiled leftover salt, so its the water from the vinegar and whats created in the reaction. So I am going to attempt to try recrystallization (with me it will take many trys but I'll get it) and see what the purity looks like after that.

Offline Yggdrasil

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Re: intro and question
« Reply #4 on: April 01, 2007, 08:47:03 PM »
If you want to do experiments with supersaturation, you could also try using table salt (NaCl) or table sugar (sucrose).  In fact, to make rock candy, people make supersaturated sugar solutions then let it crystallize.

Offline avjazz78

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Re: intro and question
« Reply #5 on: April 01, 2007, 11:08:48 PM »
Aw that takes the fun out of it :) Yeah those were a last resort but right now I can't get pure enough Sodium Acetate to do it right.

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