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CH 337 Midterm 1 OSU General questions
Terms in this set (12)
What aspects about a compound can be established from its melting point?
How is Melting behavior affected by use of too much sample?
Increase in melting point and a broadening of the temperature range at which the compound melts.
What is the likely consequence of allowing a reflux to proceed too vigorously?
Loss of reagent/products
Give the three most important attributes of an ideal solid-liquid extraction solvent
1. The desired component should be highly soluble in the solvent while the other components of the sample should not be soluble in the solvent and 2.The solvent should not react chemically in an undesirable manner with the components of the mixture and 3. after the extraction, the solvent should be readily separable from the solute
In the context of recrystallization what consequences are associated with rapid crystal growth?
The resulting sample will be less pure
What are the four principle categories of weak intermolecular interactions ranked from strongest to weakest?
Strongest: Hydrogen Bonding
2. Dipole-Dipole interactions
3. Dipole induced dipole interactions
Weakest: Induced dipole-induced dipole interactions
Why is it advisable to set aside a small amount of the crude material before performing a recrystallization?
For use as seed crystals if required
In order to obtain a purer sample through recrystallization what must be true about the impurities?
The impurities must dissolve in the hot solvent and remain in solution even as the hot saturated solution is cooled
Give the three most important attributes of an ideal recrystallization solvent
1. Chemically Inert 2. High capacity for solute of interst at bp and low capacity for solute of interest at just above freezing point
Why do most organic reactions require a period of heating?
The rxn is too slow at room temp
During distillation, how does the composition of the liquid remaining in the distilling flask change?
The liquid remaining in the distilling flask becomes richer in the less volatile component
What useful adage can guide one during the trial and error process of selecting a suitable recrystallization solvent?
Like dissolves like
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