Cryoscopic osmometry relies on which principle?

Cryoscopic osmometry relies on which principle?

• A. The temperature at equilibrium is a function of the number of particles in solution
• B. The temperature plateau for a solution is horizontal
• C. The freezing point is absolute
• D. Initial freezing yields instant solid state

Answer: (A)

Cryoscopic osmometry hinges on the fact that the temperature at which a solution freezes (the equilibrium freezing point) depends on how many dissolved particles are in the solution. This is a colligative property: the more solute particles present, the more the freezing point is depressed. By accurately measuring the freezing point of the solution, you can infer its particle concentration (and thus its osmotic concentration). The other statements aren’t the principle: a frozen-state plateau isn’t the driving concept here, freezing points aren’t absolute for solutions (they’re depressed below 0 °C), and the idea of instant solid formation at the moment of freezing doesn’t describe how cryoscopic measurements work.

Cryoscopic osmometry hinges on the fact that the temperature at which a solution freezes (the equilibrium freezing point) depends on how many dissolved particles are in the solution. This is a colligative property: the more solute particles present, the more the freezing point is depressed. By accurately measuring the freezing point of the solution, you can infer its particle concentration (and thus its osmotic concentration). The other statements aren’t the principle: a frozen-state plateau isn’t the driving concept here, freezing points aren’t absolute for solutions (they’re depressed below 0 °C), and the idea of instant solid formation at the moment of freezing doesn’t describe how cryoscopic measurements work.