Types of Chemical Reactions

There are many ways in which elements and compounds can react to form other species;
memorizing every reaction would be impossible, as well as unnecessary. However, nearly every
inorganic reaction can be classified into at least one of four general categories.

SYNTHESIS REACTIONS

Synthesis reactions are reactions in which two or more reactants form one product. The formation
of sulfur dioxide by burning sulfur in air is an example of a synthesis reaction.

S   (s) +   O 2     (g) →   SO 2    (g)

The letters in parentheses designate the phase of the species: s for solid, g for gas, l for liquid, and
aq for aqueous solution.

DECOMPOSITION REACTIONS

A decomposition reaction is defined as one in which a compound breaks down into two or more
substances, usually as a result of heating. An example of a decomposition reaction is the breakdown
of mercury (II) oxide (the sign ∆ here represents the addition of heat).

SINGLE DISPLACEMENT REACTIONS

Single displacement reactions occur when an atom (or ion) of one compound is replaced by an
atom of another element. For example, zinc metal will displace copper ions in a copper sulfate
solution to form zinc sulfate.