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How many grams of Urea would you have to dissolve in 500ml of H2O in order for the mass percent of H2O to be 88.8%? What is the mole fraction of Urea? What are the new boiling and freezing points?

  • chemistry -

    88.8% urea means 88.8g urea/100 g soln.
    I would set up
    [xgrams urea/(500g H2O + x g urea)] = 0.888
    Solve for x to obtain grams urea needed.
    moles fraction = moles urea/total moles.

    Plug this information into
    delta T = Kf*m and
    delta T = Kb*m. You will need to convert mass percent to molality.

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