In osmosis, water diffuses from area of

• A. High water concentration to low water concentration
• B. Low water concentration to high water concentration
• C. High solute concentration to low solute concentration
• D. Equal solute concentrations on both sides

Answer: (A)

Osmosis is the diffusion of water across a selectively permeable membrane from where there is more free water to where there is less free water. More solute means less free water, so water moves toward the side with higher solute concentration. That makes the movement from high water concentration to low water concentration the correct description. Moving from low to high water concentration would require water to move against its gradient, which doesn’t happen spontaneously, and diffusion of solutes is not osmosis. When solute concentrations are equal, there is no net water movement.