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Chemistry Forums for Students => High School Chemistry Forum => Topic started by: Misha on May 16, 2005, 10:07:17 PM

Title: what are 'mole fractions'?
Post by: Misha on May 16, 2005, 10:07:17 PM

I have a problem that states the following:
Calculate the mole fractions in a solution that is made of 25.0 g of ethyl alcohol, C2H5OH and 40.0g of water.

My question is, what are 'mole fractions'?

Title: Re:Mole Fractions?
Post by: Mitch on May 16, 2005, 10:48:31 PM

Well first convert everything from gams to moles and then we'll move on from there.

Title: Re:what are 'mole fractions'?
Post by: Borek on May 18, 2005, 06:12:29 AM

Less then 30 seconds using CASC  :)

Molar fraction: express amount of every substance in solution in moles. Sum the moles. Divide moles of substance by the total moles of all substances - that's the molar fraction.

Title: Re:what are 'mole fractions'?
Post by: Nano on May 18, 2005, 07:06:14 PM

mole fraction is like partial pressure in gas?
a quick thought :-X

Title: Re:what are 'mole fractions'?
Post by: Borek on May 18, 2005, 07:12:24 PM

There is some analogy. The main difference is that sum of all molar fractions is always 1, while the sum of partial pressures is just total pressure.

Title: Re:what are 'mole fractions'?
Post by: Nano on May 19, 2005, 06:05:25 PM

Quote from: Borek on May 18, 2005, 07:12:24 PM

There is some analogy. The main difference is that sum of all molar fractions is always 1, while the sum of partial pressures is just total pressure.

Learn a new lesson, thanks!