Freezing point depression is used to measure osmolality when volatile substances are suspected. Which statement describes the method?

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Freezing point depression is all about how the solvent’s temperature at which it freezes drops when solutes are present. This change in freezing point is a direct consequence of having dissolved particles, and it scales with how many particles are in solution (the molality, times the solvent’s cryoscopic constant). So, you determine osmolality by measuring the temperature at which the solvent in the mixture freezes and comparing it to the pure solvent’s freezing point. The larger the depression, the higher the osmolality.

This approach is especially useful when volatile substances are involved because volatility can throw off measurements that rely on vapor pressure or refractive index. Those methods can be biased by evaporation or changes in optical properties, whereas freezing point depression depends on particle concentration, not volatility, making it a more reliable way to estimate osmolality in such cases.