Osmotic pressure is defined as the pressure that would have to be applied to a pure solvent to prevent it from passing into a given solution by osmosis.

Osmotic pressure is defined as the pressure that would have to be applied to a pure solvent to prevent it from passing into a given solution by osmosis.

• A. The pressure exerted by the solute on the solvent
• B. The pressure that would have to be applied to a pure solvent to prevent osmosis into the solution
• C. The total pressure in the system
• D. The atmospheric pressure at which osmosis occurs

Answer: (B)

Osmotic pressure is the pressure difference that must be applied to the pure solvent side to stop the net flow of solvent into a solution across a semipermeable membrane. The presence of solute lowers the solvent’s chemical potential in the solution, so solvent would naturally move into the solution until an opposing external pressure is applied equal to this osmotic pressure. That’s why the correct description is the pressure you would apply to the pure solvent to prevent osmosis into the solution. The concept isn’t about pressure exerted by the solute itself, nor about the total system pressure or atmospheric pressure; osmotic pressure is the specific external pressure needed to counteract the solvent’s movement driven by solute concentration.

Osmotic pressure is the pressure difference that must be applied to the pure solvent side to stop the net flow of solvent into a solution across a semipermeable membrane. The presence of solute lowers the solvent’s chemical potential in the solution, so solvent would naturally move into the solution until an opposing external pressure is applied equal to this osmotic pressure. That’s why the correct description is the pressure you would apply to the pure solvent to prevent osmosis into the solution. The concept isn’t about pressure exerted by the solute itself, nor about the total system pressure or atmospheric pressure; osmotic pressure is the specific external pressure needed to counteract the solvent’s movement driven by solute concentration.