Difficulty: Easy

Average Score: 100%

Why does osmosis require a selectively permeable membrane?

Rationale

It is necessary to produce a concentration gradient of solute.

Osmosis is the process by which water molecules move from an area of lower solute concentration to an area of higher solute concentration, in order to balance the concentrations on both sides of a membrane. For osmosis to occur, a selectively permeable membrane is necessary to create and maintain a concentration gradient of solute.

A (It prevents water from moving across it) YOUR ANSWER

This is incorrect because a selectively permeable membrane actually allows water to move across it. The goal of osmosis is to equalize the solute concentration on both sides of the membrane. This would not be possible if the membrane prevented water from moving across it.

B (It prevents osmotic pressure from increasing) YOUR ANSWER

The purpose of the selectively permeable membrane is not to prevent osmotic pressure from increasing. In fact, osmotic pressure is the result of water moving from an area of lower concentration to an area of higher concentration. This pressure is a direct result of osmosis, not a factor that the membrane is trying to prevent.

D (It prevents hydrostatic pressure from increasing) YOUR ANSWER

The selectively permeable membrane does not prevent hydrostatic pressure from increasing. Hydrostatic pressure is the pressure exerted by a fluid due to gravity. It can influence osmosis, but it is not directly controlled by the membrane. The membrane's primary role is to facilitate the movement of water to balance solute concentrations.

Conclusion

A selectively permeable membrane is crucial in osmosis to establish a solute concentration gradient. It does not prevent water movement or the increase in osmotic or hydrostatic pressure. Instead, it allows water to move from an area of lower solute concentration to an area of higher solute concentration, thereby equalizing the solute concentrations on both sides of the membrane. This is the fundamental principle of osmosis.

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