simple & vacuum distillation

[inaccensa]

Advertisement - Members don't see this ad

There are 2 solvents that are being separated. I understand that the first solvent will not boil at its true temp, since it's vapor pressure has decreased. Does the second solvent boil at its true boiling temp? Lets say one boils at 30c and other at 100C. so the solvent A will may be boil at 35C, but will solvent B boil at 100c or higher, assuming that there are no other impurities.

 

[gbu730]

There are 2 solvents that are being separated. I understand that the first solvent will not boil at its true temp, since it's vapor pressure has decreased. Does the second solvent boil at its true boiling temp? Lets say one boils at 30c and other at 100C. so the solvent A will may be boil at 35C, but will solvent B boil at 100c or higher, assuming that there are no other impurities.

Not sure if I understand your question, but two things to consider:

1. (Ideally) Since temperature does not change during evaporation, solvent A with the lower bp gets boiled off first. Then you'll be left with solvent B, assuming no impurities.

2. If you look at one of those phase diagrams involving a solution mixture, you'll see that the vapor pressure/bp changes--as vaporization of solvent A takes places, the composition of the mixture changes, so does the bp. This becomes a more complicated problem that you wouldn't need to worry about for the MCAT.

I hope this helps and I didn't confuse you more! 🙂

 

[redlight]

neither boil at the true temp. the vacuum affects both liquids. it saves you time on evaporating for liquids with high boiling points.. it isn't the best for separating liquids with similar boiling points. it just makes it faster to boil off and collect the liquids.