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Vapor Pressure of Solutions

  • Thread starter Ki-nana18
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Homework Statement



An aqueous CaCl2 solution has a vapor pressure of 82.3 mmHg at 50 degrees C. The vapor pressure of pure water at this temperature is 92.6 mmHg. What is the concentration of CaCl2 in mass percent?


Homework Equations


mass %=(mass of component/total mass)*100%
Psolution=XH2OPH2O


The Attempt at a Solution


I know I have to use Raoult's Law in order to compute the mole fraction but I'm not sure what to do after. Once I have mole fraction what do I do?
 

Answers and Replies

  • #2
Borek
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Assume 1L of the solution. Molar fraction of CaCl2 is x, molar fraction of water is 1-x. Write definition of molar fraction, write how does the mass depend on number of moles for solvent and for solute. Mass of solvent plus mass of solute is a mass of 1L of solution. Assume density of 1 g/mL. That will give you a set of equations, you should be able to solve them for mass of solute and mass of solvent.
 

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