LAB PROCEDURES
Methods of Separation
Filtration—In filtration, solids are separated from liquids as the mixture is
passed through a filter. Typically, porous paper is used as the filter. To find
the amount of solid that is filtered out of a mixture, the filter paper
containing the solid is allowed to dry and is then weighed. The initial
weight of the clean, dry filter is then subtracted from the weight of the
dried filter paper and solid.
Distillation—In distillation, the differences in the boiling points of liquids can
be used to separate them. The temperature of the mixture is raised to a
temperature that is greater than the boiling point of the more volatile
substance and lower than the boiling point of the less volatile substance.
The more volatile substance will vaporize, leaving the less volatile
substance as a liquid.
Chromatography—In chromatography, substances are separated by the
differences in the degree to which they are adsorbed onto a surface. The
substances are passed over the adsorbing surface, and the ones that stick to
the surface with greater attraction will move more slowly than the
substances that are less attracted to the surface. This difference in speeds is
what separates the substances.
Titration
Titration is one of the most important laboratory procedures. In titration, an acid-
base neutralization reaction is used to find the concentration of an unknown acid
or base. It takes exactly 1 mole of hydroxide ions (base) to neutralize 1 mole of
hydrogen ions (acid), so the concentration of an unknown acid solution can be
found by finding out how much of a known basic solution is required to
neutralize a sample of given volume. The most important formula in titration
experiments is derived from the definition of molarity.