Question

Semi Microscale Crystallization

This experiment investigated the extraction of pure sulfanilamide from an impure crystallized form using 95% ethyl alcohol as a solvent.

Result (organic chemistry lab crystallization)

color: whitecrystals

M.P range of purified Sulfanilamide - 155~164℃

Weight of Impure Sulfanilamide - 0.8g

Weight of recovered Sulfanilamide - 0.36g

% recovery - 45%

QUESTIONS

1. a.Comment on the purity of your recrystallized sulfanilamide—what evidence do you have that is pure or impure? EXPLAIN

b. Why was the ‘mother liquor’ of the recrystallization yellow?

Answer 1

Ans: a The purity of the synthesised sulfanilamide can be checked by checking it's melting point .As present in the literature the m.p. of this compound is 164-165 degree Celsius. And we obtained the same experimentally so it is pure. But in addition to these purity is elucidated by various spectroscopic techniques like NMR, IR Mass Spectrometry etc. Manually checking of m.p. by capillary tube method , there may be chances of some error but these Spectroscopy tells exact nature of compounds along with impurity information.

Ans: b The mother liquor of recrystallization is yellow that may be due to presence of impurity or we can say unreacted reactant along with the desired product, like nitrobenzene is starting material for its synthesis and that is yellow in colour.