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The vapor pressure of pure water at 25 °C is 23.8 torr. Determine the vapor pressure (torr) of water
at 25 °C above a solution prepared by dissolving 35 g of urea (a nonvolatile, non-electrolyte, MW =
60.0 g/mol) in 75 g of water.

where have i made a mistake?
35g/60=0.583
75g/18.02=4.162
0.583+4.162=4.745
4.162/4.745=0.88
but my practice test says the answer is 21 where do i go wrong?
please help...

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BEN

  1. You stopped too soon.
    0.88 is the mole fraction of water. Multiply that by the normal vapor pressure of water (23.8) to obtain 20.87 which rounds to 21 mm.

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    DrBo222

  2. oops, thanks for the help!

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    BEN

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