Question

Two moles of a nonelectrolyte solute are dissolved in 1 kg of an unknown solvent. The solution freezes at 7.8 degrees Celsius below its normal freezing point. What is the molal freezing point constant of the unknown solvent? What is your prediction for the identity of the solvent?

Answer 1

m = moles/kg solvent
m = 2/1 = 2m

delta T = Kf*m
7.8 = Kf*2
Kf = 7.8/2 = ??
Here is a list of constants. Pick yours.
http://en.wikipedia.org/wiki/Freezing-point_depression

Answer 2

-3.9

Answer 3

Hey, you devide it by 4 not 2, because the number of moles are 2 plus the molality is also 2. and daltatf= kf x m x n for ionic compounds. Answer = 1.95 C

Answer 4

The Givens are :
mol(solute)=2mol
Nonelectrolyte (no. of ion=1)
mass(solvent)=1kg
tf(solution)=7.8c
The Unknown is :
Kf=?
Because it says make the solution freez lower than normal freezing point (which is 0c) so the answer should be in negative, right ??