The following reaction shows the production of hydrogen gas from water. this chemical reaction should be classified as

2 h2o 2h2 + o2

1)synthesis
2)decomposition
3)single replacement
4)double displacement
5)neutralization

This chemical reaction should be classified as a decomposition type of reaction, as basically water is decomposed using appropriate methods, chemically to produce hydrogen gas and oxygen gas. Both elements are found within the molecular formula of water. A decomposition reaction is when a compound is degraded and or broke down to form elements and other small compounds that constitute or make up the original compound.