Calculating Molarity of Ethyl Alcohol in Whiskey

[Jim4592]

Homework Statement

Eighty-six proof whiskey is 43 percent ethyl alcohol, CH₃CH₂OH, by volume. If the density of ethyl alcohol is 0.79 kg/L, what is the molarity in whiskey.

Homework Equations

Molar Mass of CH₃CH₂OH = 46.07 g

The Attempt at a Solution

0.79 kg/L * 1000 g/kg * 1 mole / 46.07 g = 17.15 M

I was just looking for a check on this particular problem since I haven't taken a chemistry course since my freshman year ha!

 

[Borek]

Not bad - you are on the right track - but wrong. You have not used 43% in your calculations and this is an important information.

 

[Jim4592]

I thought you would have to use that 43% in there somewhere, but I'm not sure how to use it. It would be nice if I still owned my chem book.

UPDATE:

Ok I tried re-working the problem again, here's what I came up with:

0.79 kg/L * 0.43 L / 1 L * 1000 g / 1 kg * 1 mol / 46.07 g = 7.37 M

how does that look?

 

[Borek]

Much better.