Combination Reactions

One of the simplest types of redox reactions is the combination reaction. In these reactions, which involve the "combining" of two elements to form a chemical compound, one element is always oxidized, while the other is always reduced as illustrated below.

Example - Formation of water from hydrogen and oxygen gas.

 

Note: Hydrogen is oxidized and oxygen is reduced.

 

Example - Formation of sulfur trioxide from oxygen and sulfur.

 

Note: Sulfur is oxidized; oxygen is reduced.