recrystallization

Question 1

what are the criteria for choosing a good solvent for recrystallization

Answer 1

1. Solvent should not chemically react with desired compounds
2. solvent should dissolve compound when hot (remember like dissolves like)
3. solvent should NOT dissolve compound when cold
4. solvent should either dissolve all the impurities at all temperatures OR not dissolve impurities at all

Question 2

what is the purpose of preheating the buchner funnel

Answer 2

to prevent the compound from recrystallizing inside the funnel

Question 3

what is the purpose of heating the solvent in recrystallization and why is that important

Answer 3

1. Heating the solvent allows us to use as little solvent as possible to dissolve the compound
2. using minimal solvent allows for maximum recovery at the end

Question 4

what does hot vaccum filtration remove

Answer 4

undissolved impurities

Question 5

how does the rate of cooling of the solution effect purity

Answer 5

the slower the solution cools, the purer it will be

Question 6

do impurities cause melting points to depress or increase

Answer 6

depress

Question 7

do pure samples of compounds have a larger or smaller melting point range

Answer 7

smaller melting point ranges

Question 8

main thing that effected our melting point

Answer 8

we took “wet” melting points, so our samples included water