Combination Reaction Definition

Stylized combustion graphic
Some combustion reactions are combination reactions.

Jose A. Bernat Bacete, Getty Images

by Anne Marie Helmenstine, Ph.D.
Dr. Helmenstine holds a Ph.D. in biomedical sciences and is a science writer, educator, and consultant. She has taught science courses at the high school, college, and graduate levels.
Updated July 08, 2019

A combination reaction is a reaction where two reactants are combined into one product. A combination reaction is also known as a synthesis reaction. The reaction has the following general form:

X + Y → XY

Combination Reaction Examples

Recognize a combination reaction by examining the number of reactants and products. In this reaction, two reactants become a single product. Combination reaction may occur between two elements, two compounds, or between a compound and an element.

The burning of carbon in the presence of oxygen to produce carbon dioxide is a combination reaction:

C + O2 → CO2

Magnesium oxide combines with carbon dioxide to form magnesium carbonate in a combination reaction:

MgO + CO2 → MgCO3