Problem: Which of the following aqueous solutions would be expected to have the lowest freezing point? A) 0.400 m K2SO4 B) 0.400 m NaCl C) 0.400 m C6H12O6 (glucose) D) 0.040 m K2SO4 E) 0.040 m NaCl

FREE Expert Solution

We’re being asked to determine the solution that has the lowest freezing point


Recall that the freezing point of a solution is lower than that of the pure solvent and the change in freezing point (ΔT­f) is given by:


ΔTf=Tf, solution-Tf, pure solvent


The change in freezing point is also related to the molality of the solution:


ΔTf=imKf


where: 

i = van’t Hoff factor

m = molality of the solution (in m or mol/kg)

Kf = freezing point elevation constant (in ˚C/m) of the solvent


The problem states that we have aqueous solutions which means the solvent is water


Therefore, ΔTf will just depend on the osmolality of each solution, given by:


Osmolality=i×m


higher osmolality or concentration will result in a lower freezing point.


  • 0.4 m K2SO4

The molality of the solution is 0.40 m. K2SOis an electrolyte that dissociates in the following manner:

K2SO 2 K+ + SO42-

The dissociation formed a total of 3 ions which means i = 3. Solving for osmolality:

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Problem Details

Which of the following aqueous solutions would be expected to have the lowest freezing point? 

A) 0.400 m K2SO4

B) 0.400 m NaCl 

C) 0.400 m C6H12O6 (glucose) 

D) 0.040 m K2SO4 

E) 0.040 m NaCl

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