Question

Suppose we add 0.001M glucose to one side of an osmometer and 0.001M hemoglobin to the other side. Will the water change? Why or why not?

Answer 1

If we consider first that only a solute is placed, say hemoglobin. Initially, the height of the fluid is the same on both sides of the osmometer, just as when no solute was present. But whereas before the solute occupied a small volume on the bench-top, now it is able to move freely throughout one side of the osmometer. There has been a large increase in the entropy of the solute. We require that the solute particles be free to roam about the entire volume on their side of the membrane, but that they not be able pass through the membrane. And just as a confined gas pushes against the walls of its container, the solution pushes against the atmosphere and against the walls of the osmometer. What happens? There is a net transfer of solvent from the side where no solute is present to the other side. This decreases the volume of pure solvent and increases the volume of solution.

Considering the above, we have water that has hemoglobin will go to the water with glucose and water containing glucose will pass the membrane into the water with hemoglobin, so the water will change at the micro level, but will not be noticeable at the macro level.