P. Chemistry
posted by Tommy on .
Can anyone direct me on how to solve this problem? All of the variables are makin my head spinnot sure how to organize them. If you can give equations to use that would help.Thnx!
1 L of an impure water solution has a freezing point of 11 °C. Which of the following is the
best estimate of the vapor pressure of the solution at 25 °C? Assume the vapor pressure of pure
water at 25oC = 23.76 atm, kF = 2 (K kg)/mol, and that water is 55 mol/L. Assume the density of
water is 1 g/mL.

delta T = Kf*molality
11 = Kf*m
Calculate m
molality = moles/kg solvent.
I think we must assume 1 kg solvent although that won't be exactly right.
Calculate (estimate) # moles.
#moles + 55.5 for H2O = total moles.
Calculate mole fraction water,
Then vapor pressure H2O = mole fraction water x 23.76 BUT I don't think that is atm (It must be torr or mm Hg). This would be an estimate at best. Check my thinking.