[INeedSerotonin]

An aqueous solution of sucrose is put in contact with equal volume of an aqueous solution of NaCl. This results in the following equilibrium:



Based on the image above, one can affirm that

A) the osmotic pressure of sucrose is greater than the NaCl's osmotic pressure
B) the molality of the NaCl solution is greater than the sucrose solution;
C) the solution of NaCl has a lower boiling point than the sucrose solution
D) both solutions, when they are found at the same temperature, will have the same vapor pressure;
E) the solution of NaCl has a lower freezing point than the sucrose solution.

Could you guys guide me in this one? I thought that (B) should be true, because it seems that water is flowing towards the NaCl solution. If it is so, then the concentration (be it molarity or molality) should be higher on NaCl. But at the same time I was told the answer is (E), so I'm confused.

Or, perhaps, at the exact moment of the image, both concentrations have become equal, and so the osmotic pressure of both have become the same, meaning that all that matters for colligative properties is the Van't Hoff coefficient. Is this correct?

Thanks

[AWK]

Osmotic pressure depends on the concentration of dissolved species. In the case of NaCl, this is not sodium chloride concentration, but doubled NaCl concentration, i.e. NaCl concentration must be greater than half of the sugar concentration for the picture to be true. The freezing-point depression depends on the same expressed concentrations (concentration of dissolved species), i.e. higher osmotic pressure corresponds to a greater lowering of freezing point. It is worth starting to solve problems from the theoretical part.
http://www.vivo.colostate.edu/hbooks/pathphys/topics/osmosis_eg.html

[INeedSerotonin]

Thanks! I solved all those problems.

I'm still confused as for why (B) could not be the answer. If there is a higher concentration on the NaCl solution, then shouldn't (B) be true?

[AWK]

The concentration of species means the sum of concentrations Na⁺ and Cl^-

[INeedSerotonin]

The concentration of species means the sum of concentrations Na⁺ and Cl^-

Ohhh I think I got it now! Thank you!