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rajan

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something i wrote about coke & whiskey
« on: December 23, 2008, 11:53:39 AM »
i figured i post this here for your entertainment and to see if i made any errors. the figure is from mathematica, and the overall pdf was made using pdflatex, which is why it looks so awesome (i take no credit for the awesomeness of latex).

http://www.tc.umn.edu/~rajan/coke.pdf

Please let me know if you see errors. First time posting here and I was pleasantly surprised to find a forum like this one.

Rabn

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Re: something i wrote about coke & whiskey
« Reply #1 on: December 24, 2008, 08:20:08 PM »
Well, I would like to propose something much less complicated. Coke is carbonated by taking advantage of the decomposition:

H2CO3  H2O + CO2

Since the acidity of whiskey isn't that different from soda you can basically use straight equilibrium:

[H2CO3] = [H+][HCO3-]/Ka

Keq = [CO2]Ka/[H+][HCO3-]

[CO2] = (Keq[H+][HCO3-])/Ka

From this equation we can see that as the volume of liquid increases and [HCO3-] decreases, [CO2] decreases.  Adding ice further decreases [CO2] as it melts because of the change in [H+] that accompanies it.  Since [CO2] is decreased after you add whiskey, you don't feel the fizz as strongly in your mouth.  The seemingly flat coke is produced by the interaction of both the Keq of decomposition and the Ka
of carbonic acid.

Rabn

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Re: something i wrote about coke & whiskey
« Reply #2 on: December 24, 2008, 10:21:18 PM »
Oh, I would also like to add that as the solution becomes less polar, the carbon dioxide bubbles would be smaller due to a smaller hydrophobic effect.

I really don't know how accurate your description is, I'm just a big fan of qualitative reasoning.

Cheers

Hunt

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Re: something i wrote about coke & whiskey
« Reply #3 on: December 25, 2008, 07:29:09 PM »
Well I've only recently begun studying the chemistry of surfaces and interfaces, so Im still a newbie. I will comment on this later. Thanks for sharing rajan.

rajan

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Re: something i wrote about coke & whiskey
« Reply #4 on: December 30, 2008, 12:55:48 AM »
thanks for the replies Rabn and Hunt... i like your argument Rabn, as it can be easily tested. next time i add some whiskey, i will add the same amount of water to a similar sample of coke. hopefully i'm not too far into my "experiment" by then and i will have some "data."

also, i believe your second post is a different way of saying something similar to my argument that the surface tension is altered.

sorry for the delayed response (i thought i would be emailed upon replies being posted).