Old ass midterm

Question 1

why is acetone is a good solvent to use for rinsing out glassware as part of the cleaning process?

Answer 1

1. acetone dissolves most organic materials
2. acetone is miscible with water
3. acetone evaporates quickly

Question 2

randy grant recrystallized 0.321 g of crude sulfanilamide from 95% ethanol. Being stoned and careless, he walks into the roto vap and drops his sample on the floor. He sweeps up the crystals, along with some dirt, sand and little pieces of bud. How can Randy re-purify the sulfanilamide and get smart?

Answer 2

Randall should dissolve the mixture in boiling 95% ethanol, and filter out the insoluble dirt, sand, bud, etc. If necessary, randy can evaporate excess solvent, or add additional boiling solvent to achieve saturation. After letting the solution cool slowly to room temperature and chilling the solution in an ice bath, vacuum filtration
will produce pure sulfanilamide. Any trace organic impurities will stay in mother liquor.

Question 3

Ims had tested her sulfanilamide melting range to be 161.6 – 163.2 °C. The literature M.P. for sulfanilamide = 165 – 167 °C. Was Ima’s sulfanilamide pure?

Answer 3

Yes.The mp is lower than the literature value, but the range is still very narrow—if the sample was impure the melting range would be significantly broadened.
Ima’s sample was pure sulfanilamide, the lowered range is most likely due to an uncorrected (uncalibrated) melting point apparatus.