[Del_Lep]

Hey guys,

I am attemping to find out the concentration of ethanol present in a 37.5% solution of Vodka. By using n=m/M I figure the concentration of ethanol should be 8.15molL-1 (375 ml in 1L, M of ethanol=46, 375/46=8.15) Is this correct?

I'm also trying to figure it out by reacting the vodka with dichromate and titrating the leftover dichromate against a thiosulfate solution. I figured the mol of ethanol that reacted with the S2O3 which is 0.0159732. That was in a 5ml sample of 5ml 37.5% vodka, 995 ml water solution. From this what is the concentration of the original solution? My calculations:

.015 x 200 = 3.19 -> mol of diluted 1L solution
3.19 x 200 = 638.928 -> mol in original 37.5% solution

Obviously this is wrong, what I want to know is it because of these calculations of the dilutions above or must it be something I did before hand, when I calculated the mol of ethanol that reacted with S2O3?

Thanks for your help.

[Borek]

I am attemping to find out the concentration of ethanol present in a 37.5% solution of Vodka. By using n=m/M I figure the concentration of ethanol should be 8.15molL-1 (375 ml in 1L, M of ethanol=46, 375/46=8.15) Is this correct?

Volumes are not additive. Is it w/w, w/v or v/v percentage?

http://www.chembuddy.com/?left=concentration&right=toc

[Del_Lep]

If it's w/v, then is it right? It most likely is v/v, I'll have to look tomorrow.

I'm trying the calculations again, any chance you know the general concentration of a 37.5% vodka solution (in molL-1)? It;'s hard to do the calculations and don't know what the answer should be close to, as I have no idea if I've screwed something up.