The partial water vapor pressure over the soulution of glucose (C6H12O6) in water is 715 torr at 100 degrees celsius. Find freezing temperature of this solution.

Answer 1

well, you certainly know the vapor pressure of water at 100C is 760 torr.

Partial pressure of water is in accorance with the mole ratio, so

715/760=moleswater/totalmoles

715/760=moleswater/(molessugar+molewater)

molality=molessugar/1000kgwater
molality=molessugar/(moleswater*18)

take the first equation, solve for moles sugar/moles water, put it in the second equation, and you should have it.