Question

Solutions A and B are separated by a semipermeable membrane. Solution A contains 1mM sucrose and 1mM urea. Solution B contains 1mM sucrose. The reflection coefficient for sucrose is one and the reflection coefficient for urea is zero. Which of the following statements about these solutions is correct?

1) Solution A has a higher effective osmotic pressure than solution B
2) Solution A has a lower effective osmotic pressure than solution B
3) Solutions A and B are isosmotic
4) Solution A is hyperosmotic with respect to solution B, and the solutions are isotonic
5) Solution A is hyposmotic with respect to solution B, and the solutions are isotonic

Answer 1

The Correct option is 3). Solution A and solution B are isosmotic because they both contain an equal concentration of sucrose, which is the solute that can't cross the semipermeable membrane and affects the osmotic pressure.

Step-by-step explanation:

In this scenario, solution A contains 1mM sucrose and 1mM urea, while solution B contains only 1mM sucrose. The reflection coefficient for sucrose is one, which means it cannot cross the semipermeable membrane and will exert full osmotic pressure. However, the reflection coefficient for urea is zero, indicating it can freely cross the membrane and will not contribute to the osmotic pressure.

Solutions A and B both have an equal concentration of sucrose, therefore they have the same osmotic pressure due to sucrose. Since urea can cross the membrane and does not affect the osmotic pressure, the presence of urea in solution A does not give it a higher effective osmotic pressure compared to solution B. Thus, the correct statement regarding these solutions is that Solutions A and B are isosmotic.