Colligative properties...

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A semipermeable membrane separates an aqueous solution of 0.003 M NaCl from an aqueous solution of 0.0025 M BaF2. With this apparatus, one would observe that water crosses the membrane:


A.
from the BaF2 solution to dilute the NaCl solution.


B.
from the NaCl solution to dilute the BaF2 solution.


Correct Answer

C.
from the BaF2 solution to concentrate the NaCl solution.


D.
from the NaCl solution to concentrate the BaF2 solution.

Explanation:

B. Osmotic pressure is a colligative property, which means it depends only on the concentration of solute particles, and not their identity. Therefore, a 0.003 M solution of NaCl will have an effective molality of 0.006 M (since NaCl is composed of two ions) and a 0.0025 M solution of BaF2 will have an effective molality of 0.0075 M (since BaF2 is composed of three ions). Osmotic pressure will drive movement of water from the lower concentration solution (NaCl) to the higher concentration solution (BaF2). Note that this movement of water acts to dilute the BaF2 solution.



I think their answer is wrong...and I think this explanation support my answer...Am I correct?

Originally Posted by BestDoctorEver

A semipermeable membrane separates an aqueous solution of 0.003 M NaCl from an aqueous solution of 0.0025 M BaF2. With this apparatus, one would observe that water crosses the membrane:


A.
from the BaF2 solution to dilute the NaCl solution.


B.
from the NaCl solution to dilute the BaF2 solution.


Correct Answer

C.
from the BaF2 solution to concentrate the NaCl solution.


D.
from the NaCl solution to concentrate the BaF2 solution.

Explanation:

B. Osmotic pressure is a colligative property, which means it depends only on the concentration of solute particles, and not their identity. Therefore, a 0.003 M solution of NaCl will have an effective molality of 0.006 M (since NaCl is composed of two ions) and a 0.0025 M solution of BaF2 will have an effective molality of 0.0075 M (since BaF2 is composed of three ions). Osmotic pressure will drive movement of water from the lower concentration solution (NaCl) to the higher concentration solution (BaF2). Note that this movement of water acts to dilute the BaF2 solution.



I think their answer is wrong...and I think this explanation support my answer...Am I correct?

B is correct and the explanation supports answer B.

Originally Posted by MedPR

B is correct and the explanation supports answer B.

Sorry...My gosh...did not read carefully the answer...I hate that. I thought B said: (from the NaCl solution to the diluted BaF2 solution)