Question

Which of the following solutions will have the lowest freezing point? a.) KF (aq) 0.50m b.) glucose soln (0.60m) c.) sucrose soln (0.60m) d.)FeI3 (aq) (0.24 m)

If you could PLEASE EXPLAIN that would be great! Thank you

Answer 1

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.)
• 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 KF, 4 for FeCl_3, and 1 for glucose and sucrose).

So, ΔT_F will be hihgest for the KF solution and hence it will have the lowest freezing point.