[AirForceOne]

"Calculate the freezing point of an aqueous solution that boils at 100.5 C"

How do I do this? I know so far that:

BP soln = 100.5 C
FP soln = ? C
Solvent = H20

BP elevation = Temp. of solution - Temp. of pure solvent
BP elevation = 100.5 C - 0 C
BP elevation = 100.5 C

FP depression = Molal FP x molality

Im kinda stuck 

[enahs]

For boiling point elevation:
?T_b = k_b*m
Where k_b is the molal boiling point elevation constant (which you know this for water), and m is the molal concentration of the solution. You know everything in that equation but the molal concentration, solve for it.

Your freezing point depression:
?T_f = k_f*m
Where k_f, is the molal freezing point depression constant, again something you know, and you now know the molal concentration from the ?T_b , just plug into that equation.

And, btw, this is wrong:

BP elevation = Temp. of solution - Temp. of pure solvent
BP elevation = 100.5 C - 0 C
BP elevation = 100.5 C

Water boils at 100^oC, so the elevation is only 0.5^oC

[AirForceOne]

Thank you so much! Got the answer right