Homework due 2.21.17

Read
  Chapter 15.10, pp 495 - 496
Do
  Problems 50, 51, 59

Calculation of Freezing Point Depression

If the solution is treated as an ideal solution, the extent of freezing-point depression depends only on the solute concentration that can be estimated by a simple linear relationship with the cryoscopic constant ("Blagden's Law"):

ΔT_F = K_F · b · i,

where:

• ΔT_F, the freezing-point depression, is defined as T_{F (pure solvent)} − T_{F (solution)}.
• K_F, the cryoscopic constant, which is dependent on the properties of the solvent, not the solute. (Note: When conducting experiments, a higher K_F value makes it easier to observe larger drops in the freezing point. For water, K_F = 1.853 K·kg/mol.^[7])
• b is the molality (moles solute per kilogram of solvent)
• i is the van 't Hoff factor (number of ion particles per individual molecule of solute, e.g. i = 2 for NaCl, 3 for BaCl₂)