Question

A solution of 5% starch, 5% glucose and 5% salt is placed into a bag of dialysis tubing. The tubing is only permeable to water, not permeable to glucose and starch. If the bag is submerged in distilled water, what will happen to all of the molecules involved? Identify which of the original solutions was hypertonic, hypotonic, or isotonic where applicable.

Answer 1

Distilled water has no salt concentration. Thus its osmotic pressure is lower than the solution in the bag, hence the original solution is hypertonic. When the bag is submerged in distilled water, being a hypotonic solution distilled water will move inside the bag as solute concentration inside the bag is more. Thus the concentration (mole/litre) of all the solutes disolved will decrease due to the increase in concentration. The water will continue to flow inside the bag till both the solutions become isotonic, i.e when the solute concentration inside the bag will become very low.