Final answer:
Osmotic pressure is the pressure exerted by a solvent across a semi-permeable membrane to prevent the flow of solute and is considered a colligative property of solutions, representing solvent movement due to concentration differences.
Step-by-step explanation:
Osmotic pressure is defined as the pressure difference between the two sides of a semi-permeable membrane that separates a pure solvent from a solution made from the same solvent. It's a colligative property of solutions that indicates the tendency for solvent molecules to pass through a semi-permeable membrane in response to a concentration difference. The phenomenon of solvent passing through the membrane is known as osmosis, where the expected flow of solvent is from the area of lower solute concentration to the area of higher concentration. Applying an external pressure that is equivalent to the osmotic pressure of the solution can halt this process.
With reference to chemical potential osmotic pressure can thus be understood as the pressure required to prevent the bulk transfer of solvent molecules across the semi-permeable membrane brought about by the differences in chemical potential due to solute concentration variations across the membrane. Answering the student's multiple-choice question, option (a) The pressure exerted by a solvent across a semi-permeable membrane to prevent the flow of solute is the correct definition of osmotic pressure in the context of chemical potential.