CHEM 2050/2130 Quiz 1 Review Sheet
Review the front material we see in the lab experiments: the “big questions” about this quiz point to
“why” and “what” questions: i.e. why do we use . . . . , or what is the purpose of . . . .
Recrystallization:
Characteristics which are desirable for a recrystallization solvent can be found in the beginning of the
recrystallization experiment. We perform mixed melting points to ID the proper material and rules out
incorrect materials. When using a Melt-Temp, the temperature rise in the melting range, do heat too
quickly. The range of heating should be 3 – 5 degrees/minute.
Extraction:
Understand the basic idea of a distribution coefficient: In the expression Korganic/water = [A]organic/[A]water
is a measure of the tendency for the solute to reside in one phase versus the other and is equal to the
ratio of solubility’s for A in the respective solvents. Understand why the various chemicals or solutions
could be used in an extraction, for example, sodium bicarbonate (NaHCO3), HCl, NaOH, and MgSO4 or
Na2SO4
Basic Ideas for Chromatography:
In the column chromatography we use silica (SiO2) as the stationary phase, which is a solid, inert
material that contains a polar functional group. The solvent is a less polar material. We use the general
idea of solubility to separate components in a mixture: polar materials are more attracted to the
stationary phase while less polar materials are more attracted to the mobile phase. Be able to properly
calculate Rf’s.
Distillation:
Distillation is a technique used to separate mixtures into separate fractions. Some different types of
distillation include simple distillation, fractional distillation and steam distillation. Understand the
differences we see in the two types of distillation we perform in lab.