A combination reaction or a synthesis reaction is a general category of a chemical reaction (the term usually refers to an inorganic chemical reaction), in which two or more reactants are chemically bonded together to produce a single product. When two or more substances combine to form a single product, it is known as a combination reaction. Many elements react with one another in this fashion to form compounds.
This reaction is usually exothermic because when the bond forms between the reactants, heat is released.
A combination reaction can be of three types:
| Type | Example | |
|---|---|---|
| a) Between two elements | C + O2 → CO2 | Carbon completely burnt in oxygen yields carbon dioxide |
| b) Between two compounds | CaO + H2O → Ca(OH)2 | Calcium oxide (lime) combined with water gives calcium hydroxide (slaked lime) |
| c) Between an element and a compound | O + H2O → H2O2 | Oxygen (an element) combined with water (a compound) yields hydrogen peroxide |
When a combination reaction occurs between a metal and a nonmetal the product is an ionic solid. An example could be Lithium + Sulphur → Lithium Sulphide
When magnesium metal burns in air to produce magnesium oxide, a combination reaction occurs between magnesium and the diatomic oxygen molecule. This specific combination reaction produces the bright flame generated by flares.