Test 1 (slides) Flashcards
Solute
The substance that is being dissolved
Solvent
The medium in which the solute is being dissolved
Miscible
The solute and solvent form a homogeneous solution in all proportions.
Immiscible
The solute and solvent do NOT mix; they form two separate liquid phases
Higher MW organic compounds ( > 4 carbons) with hydrocarbon portions (even those with polar functional groups) are usually _______ in water
insoluble
Gas chromatography
- Stationary phase: thin film of polymer or a wax (with a high boiling point) in a tube - Mobile phase: gas (usually He, could be H2) - Key physical property: boiling point (within a functional group clas
Liquid chromatography
- Stationary phase: silica, alumina, florisil, derivatized silica, etc. - Mobile phase: organic solvents (normal phase) aqueous mixtures (reversed phase) - Key physical property: hydrogen-bonding, polarity
Stationary Phase: Silica (SiO2)
H-bonding and dipole-dipole forces
What solubility is required to have a successful crystallization?
A successful crystallization depends on a large differential solubility of the material in a given solvent with respect to temperature. (i.e. high solubility at high temperature, low solubility at low temperature)
Ideally, any impurities remain ______ in the chosen solvent at low temperature.
Ideally, any impurities remain soluble in the chosen solvent at low temperature.
Melting Point for Impure Compound
An impure compound will have a melting point that is lower and more broad than the literature value for the pure substance.
What exactly is “the boiling point” of a solution?
The ‘boiling point’ is the temperature at which: The vapor pressure above a solution EQUALS ‘atmospheric’ pressure
Simple Distillation: Apparatus
Fractional Distillation: Theoretical plates
Count the “tie-lines” (horizontal lines): it looks like about 5 plates are needed to separate this mixture
Retention time
Used to identify components by comparing retention times to known standards.
