1
Q
what are the criteria for choosing a good solvent for recrystallization
A
- Solvent should not chemically react with desired compounds
- solvent should dissolve compound when hot (remember like dissolves like)
- solvent should NOT dissolve compound when cold
- solvent should either dissolve all the impurities at all temperatures OR not dissolve impurities at all
2
Q
what is the purpose of preheating the buchner funnel
A
to prevent the compound from recrystallizing inside the funnel
3
Q
what is the purpose of heating the solvent in recrystallization and why is that important
A
- Heating the solvent allows us to use as little solvent as possible to dissolve the compound
- using minimal solvent allows for maximum recovery at the end
4
Q
what does hot vaccum filtration remove
A
undissolved impurities
5
Q
how does the rate of cooling of the solution effect purity
A
the slower the solution cools, the purer it will be
6
Q
do impurities cause melting points to depress or increase
A
depress
7
Q
do pure samples of compounds have a larger or smaller melting point range
A
smaller melting point ranges
8
Q
main thing that effected our melting point
A
we took “wet” melting points, so our samples included water
