osmosis question

[predentgal]

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A .154 M solution of NaCl is approximately isotonic with blood. What would happen to red blood cells if they were placed in a .05 M NaCl solution.?

A.Water would diffuse into the cells and they would swell.
B.Water would diffuse out of the cells and they would swell
C. Water would diffuse out of the cells and they would shrink.

The correct answer is A but I thought it was C. Water diffuses from areas of low solute to high solute. If the cells are originally in a more concentrated solution with less water, water would travel down its osmotic gradient to the more concentrated side. Once they're placed in the less concentrated solution water will leave the cell to make up for the loss of solute and to try to make the cell more concentrated so that it could be isotonic with its environment again. That's the way I learned it. Am I wrong?

 

[uclaDDS101]

The answer is A. The solute concentration inside the cell is 0.154M. Youre placing it in a 0.05M solution. As you said, water will travel from low solute concentration to high solute concentration. Therefore, water will diffuse into the cell (.05M to .154M) and it would swell.

That's the explanation. Try not to make this a complicated problem because it's a very common one (you'll probably see something similar to it on your test).