HELP! question about Simple Distillation

[coldviva204]

In one our organic chemistry labs, we had to measure the boiling point of the first evaporated liquid and then compare the measured boiling point with its literature value.

My question is that: why isn't the boiling point elevated for first evaporated liquid due to the presence of another liquid in solution?

Why is that only non volatile solid solutes can contribute to the elevation of boiling point?

I will be filled with gratitude if someone can help me with the above! Thank you!

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[thebillsfan]

it is not true that nonvolatile solutes are the only ones that affect vapor pressure. volatile solutes can as well--depending on whether its more or less volatile than the main solvent. my guess is that the bp was elevated a little bit, but in an undergrad chem lab you cant really tell--your sample is often impure anyway which messes up the boiling pt, etc

 

[wanderer]

My question is that: why isn't the boiling point elevated for first evaporated liquid due to the presence of another liquid in solution?

It is elevated. Unless you did fractional or the two compounds boiled at very different temperatures.