Calculate the freezing point of a 2.0 m solution of sucrose in water. Sucrose is a nonelectrolyte. The normal freezing point of pure water is 0.00ºC. K_f (water)= -1.86ºC/m. A)-1.86ºC B)-3.72ºC C)-2.00ºC D)3.72ºC E)1.86ºC

Question

Quizplus · Accepted Answer

The freezing point depression, ΔTf = i*Kf*m, where i is the van't Hoff factor (equal to 1 for a nonelectrolyte), Kf is the cryoscopic constant (-1.86ºC/m for water), and m is the molality of the solution (2.0 mol/kg).

ΔTf = 1*(-1.86ºC/m)*2.0m = -3.72ºC

Thus, the freezing point of the solution is:

Freezing point = normal freezing point - ΔTf

Freezing point = 0.00ºC - (-3.72ºC)

Freezing point = 3.72ºC below 0.00ºC

Therefore, the answer is B) -3.72ºC.

Calculate the Freezing Point of a 2