[YourHuckleberry]

I have the following lab problem and have been hacking away at it for so long that I think I'm making it harder than it is. Any help would be appreciated: "If the sample of acetic acid was old and had absorbed water vapor from the air so that it contained 6.0% water by mass, calculate the freezing point temperature of this solution. [Here, water is the solute. Choose an appropriate mass basis, from which you will need to calculate the mass of solute and the mass of solvent.]"

Givens: Delta Tf = -(Kf)(m); Kf of acetic acid (a.a) is 3.90 °C kg/mol; a.a freezing point is 16.6 °C

Reorganized equation: Tf(solution) = -(Kf)(m) + Tf(solvent)

I choose a solution mass of 10g (0.6g H₂O and 9.4g a.a), how does the following approach look?

m = (0.6 g H₂O)(1 mol H₂O/18.02 g H₂O)*(1/0.0094 kg a.a) + 16.6 °C = 3.54 mol H₂O per kg a.a

Tf(solution) = -(3.90 °C kg/mol)(3.54 mol/kg) + 16.6°C = 2.8 °C

[Borek]

Logic looks OK to me.