Experiment:10
Determination of the heat of precipitation
Theory
Heat of Precipitation is defined as the amount of heat liberated in the
precipitation of one mole of a sparingly soluble substance when solutions
of suitable electrolytes are mixed.
Precipitation Reactions occur when cations and anions of aqueous
solutions combine to form an insoluble ionic solid, called
a precipitate. Whether or not such a reaction occurs can be determined
by using the solubility rules for common ionic solids. Since not all aqueous
reactions form precipitates, one must consult the solubility rules
before determining the state of the products and writing a net ionic
equation.
Properties of Precipitates
Precipitates are insoluble ionic solid products of a reaction, in which
certain cations and anions combine in an aqueous solution. The
determining factors of the formation of a precipitate can vary. Some
reactions depend on temperature, such as solutions used for buffers, while
others are dependent only on solution concentration. The solids produced
in precipitate reactions are crystalline solids. This solid can be suspended
throughout the liquid or fall to the bottom of the solution. The fluid that
remains is called the supernatant liquid. The two parts (precipitate and
supernate) can be separated by various methods, such as filtration,
centrifuging, or decanting.
