Main Page | See live article | Alphabetical index In chemistry, a chemical equation is a symbolic representation of a chemical reaction. For example, the combustion of methane in oxygen is CH4 + 2 O2 → CO2 + 2 H2O, and the reversible reaction of the Haber process is N2(g) + 3H2(g) <--> 2NH3(g) + ΔH. See also: Full equation and ionic equation. This article is from Wikipedia. All text is available under the terms of the GNU Free Documentation License.