Test 1 (slides)

Question 1

Solute

Answer 1

The substance that is being dissolved

Question 2

Solvent

Answer 2

The medium in which the solute is being dissolved

Question 3

Miscible

Answer 3

The solute and solvent form a homogeneous solution in all proportions.

Question 4

Immiscible

Answer 4

The solute and solvent do NOT mix; they form two separate liquid phases

Question 5

Higher MW organic compounds ( > 4 carbons) with hydrocarbon portions (even those with polar functional groups) are usually _______ in water

Answer 5

insoluble

Question 6

Gas chromatography

Answer 6

• 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

Question 7

Liquid chromatography

Answer 7

• Stationary phase: silica, alumina, florisil, derivatized silica, etc. - Mobile phase: organic solvents (normal phase) aqueous mixtures (reversed phase) - Key physical property: hydrogen-bonding, polarity

Question 8

Stationary Phase: Silica (SiO2)

Answer 8

H-bonding and dipole-dipole forces

Question 9

What solubility is required to have a successful crystallization?

Answer 9

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)

Question 10

Ideally, any impurities remain ______ in the chosen solvent at low temperature.

Answer 10

Ideally, any impurities remain soluble in the chosen solvent at low temperature.

Question 11

Melting Point for Impure Compound

Answer 11

An impure compound will have a melting point that is lower and more broad than the literature value for the pure substance.

Question 12

What exactly is “the boiling point” of a solution?

Answer 12

The ‘boiling point’ is the temperature at which: The vapor pressure above a solution EQUALS ‘atmospheric’ pressure

Question 13

Simple Distillation: Apparatus

Answer 13

Question 14

Fractional Distillation: Theoretical plates

Answer 14

Count the “tie-lines” (horizontal lines): it looks like about 5 plates are needed to separate this mixture

Question 15

Retention time

Answer 15

Used to identify components by comparing retention times to known standards.

Question 16

Gas Chromatography Peak Area

Answer 16

Used to determine the relative amount of different components