Final answer:
If a liquid boils at a consistent temperature throughout distillation, it suggests purity, but factors like atmospheric pressure must be considered. Boiling point elevation, a colligative property, indicates the presence of a solute. Overall, purity determination requires understanding all factors influencing boiling point.
Step-by-step explanation:
If fifty milliliters of a liquid boils at 74.8°C consistently from the beginning to the end of distillation, it generally suggests that the liquid may be pure. The constant boiling point indicates no significant change in composition as the distillation progresses, which is a characteristic of a pure substance. In contrast, a mixture usually has a wide boiling range because different components vaporize at different temperatures. However, other factors could influence the boiling point, such as atmospheric pressure. The normal boiling point corresponds to a pressure of 1 atm, and deviations from this pressure can alter the observed boiling point.
When evaluating boiling point elevation, as in the equation -(0.52) (1.71 m) (2) = 1.78°C, we consider the colligative property that the presence of a solute can increase the boiling point of a solvent. A pure water boiling point increase of 1.78°C with a solute present would result in a new boiling point of 101.78°C.
Therefore, to conclude purity based on boiling point alone, one must consider all factors, including the precise atmospheric pressure during distillation and ensuring that the liquid does not contain non-volatile impurities, which would not affect the boiling point. Ultimately, a boiling point analysis should include a self-assessment to verify the consistency of the boiling point and consider the surrounding conditions.