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Zorluk: KolayPure and Impure Substances and Criteria of Purity

The presence of a soluble non-volatile impurity in a liquid sample lowers its boiling point below that of the pure liquid.

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The statement is False. Soluble non-volatile impurities elevate the boiling point of a pure liquid rather than lowering it.
A soluble non-volatile solute reduces the vapor pressure of a liquid solvent. As a result, extra thermal energy (a higher temperature) is required for the vapor pressure to equal atmospheric pressure, causing boiling point elevation.

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1
Identify the physical effect of a dissolved non-volatile impurity on liquid vapor pressure.
Dissolved non-volatile solute particles occupy surface area and reduce the vapor pressure of the solvent liquid at a given temperature.
Fewer solvent molecules can escape into the gas phase due to solute-solvent interactions and physical surface blockage.
2
Determine the impact of lower vapor pressure on the boiling point.
The liquid must be heated to a higher temperature for its vapor pressure to equal external atmospheric pressure.
Boiling occurs when vapor pressure equals atmospheric pressure, leading to boiling point elevation.

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Effect of Impurities on Boiling Point
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Pure and Impure Substances and Criteria of Purity