Suppose a lab measured serum osmolality on the same patient sample by freezing-point and vapor-pressure methods, and the osmolality measurement by the freezing-point method was found to be greater than the osmolality measurement by the vapor-pressure method.Which of the following is the most likely explanation for this discrepancy?

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Quizplus · Accepted Answer

The presence of unexpected volatile solutes is known to produce this type of discrepant result between these two methods.Vapor-pressure techniques will not detect the presence of all solutes, because volatile solutes will be measured as part of the solvent and not cause vapor-pressure depression.Ethanol is an example of a solute that will not be detected by vapor-pressure depression, because it will not suppress evaporation of solvent.Instead, because of the volatile nature of ethanol, it will add to vapor pressure produced by the solvent.Freezing-point methods will detect the presence of volatile materials like ethanol.Thus when volatile solutes are present, the two methods will produce different results.

Suppose a Lab Measured Serum Osmolality on the Same Patient