The solutions in the arms of a U-tube are separated at the bottom of the tube by a selectively permeable membrane. The membrane is permeable to sodium chloride but not to glucose. Side A is filled with a solution of 0.4 M glucose and 0.5 M sodium chloride (NaCl), and side B is filled with a solution containing 0.8 M glucose and 0.4 M sodium chloride. Initially, the volume in both arms is the same. Refer to the figure to answer the following questions.

-At the beginning of the experiment,
A) side A is hypertonic to side B.
B) side A is hypotonic to side B.
C) side A is isotonic to side B.
D) side A is hypertonic to side B with respect to glucose.
E) side A is hypotonic to side B with respect to sodium chloride.

Question

The solutions in the arms of a U-tube are separated at the bottom of the tube by a selectively permeable membrane. The membrane is permeable to sodium chloride but not to glucose. Side A is filled with a solution of 0.4 M glucose and 0.5 M sodium chloride (NaCl), and side B is filled with a solution containing 0.8 M glucose and 0.4 M sodium chloride. Initially, the volume in both arms is the same. Refer to the figure to answer the following questions.
 
-At the beginning of the experiment,
A) side A is hypertonic to side B. 
B) side A is hypotonic to side B. 
C) side A is isotonic to side B. 
D) side A is hypertonic to side B with respect to glucose. 
E) side A is hypotonic to side B with respect to sodium chloride.

Quizplus · Accepted Answer

At the beginning of the experiment, the concentration of glucose is higher in side B (0.8 M) than in side A (0.4 M). Therefore, side A is hypotonic to side B with respect to glucose. This means that water will flow from side A to side B to try to equalize the concentration of glucose. Additionally, the concentration of sodium chloride is higher in side A (0.5 M) than in side B (0.4 M). Therefore, side A is also hypertonic to side B with respect to sodium chloride. However, since the membrane is permeable to sodium chloride, the ion will be able to diffuse freely across the membrane, and there will be no net movement of water due to the difference in sodium chloride concentration. Overall, because of the difference in glucose concentration, water will flow from side A to side B, making side A hypotonic to side B.

The Solutions in the Arms of a U-Tube Are Separated