The burning of wood represents a combustion reaction.
Chemists classify chemical reactions into four or more categories based on the reaction's characteristics. The categories provide a convenient means for chemists to describe reactions and for students to predict a reaction's products. Opinions vary on the number of chemical reaction types. Some texts list only four types: combination, decomposition, replacement and double replacement. Other texts may also include combustion, acid-base and oxidation-reduction reactions. Furthermore, some reactions can be correctly categorized into two different reaction types.
Combination AB
Many metal oxides, for example, absorb carbon dioxide (CO2) from the air to form carbonates:
CaO(s) + CO2(g) ---> CaCO3(s)
Decomposition 2 H2(g) + O2(g)
Single-Replacement AX + B where X represents the atom being exchanged.
Many metals, for example, react with acids to produce hydrogen and a metal salt:
Zn(s) + 2 HCl(aq) ---> ZnCl2(aq) + H2(g)
Double-Replacement CaCO3(s) + 2 NaCl(aq)
Combustion
Combustion reactions occur when substances, particularly those containing carbon, burn in the presence of oxygen to produce carbon dioxide and water:
CxHy + O2 ---> CO2(g) + H2O(g)
Methane, for example, with chemical formula CH4 combusts as:
CH4(g) + O2(g) ---> CO2(g) + 2 H2O(g)
Tags: carbon dioxide, reaction types
