Posted by Daiyo on Friday, December 10, 2010 at 9:34am.
The normal boiling point of ethanol is 78.4°C. When 9.16 g of a soluble nonelectrolyte was dissolved in 100. g of ethanol, the vapor pressure of the solution at that temperature was 7.40 102 Torr.
(a) What are the mole fractions of ethanol and solute?
(b) What is the molar mass of the solute?
Chemistry - Daiyo, Friday, December 10, 2010 at 9:35am
The vapor pressure is actually 7.40 x 10^2
Chemistry - DrBob222, Friday, December 10, 2010 at 12:54pm
The vapor pressure of ethanol (any liquid at its boiling point) is 760 torr. So
Psoln = Xethanol*Poethanol.
Xethanol = P/Po = 740/760 = ??
Xethanol + Xsolute = 1
(b). You know 100 g ethanol. Change to moles ethanol.
nethanol/(nethanol+nsolute) = Xethanol (from a part).
Solve for nsolute(moles solute).
Then moles = grams/molar mass. Solve for molar mass.
Post your work if you get stuck.
Chemistry - Daiyo, Friday, December 10, 2010 at 4:10pm
Thanks for the help DrBob
I forgot the pressure of any liquid at boiling point
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