All combination reactions involve oxygen

No sources are cited in this article. Please help improve this article by adding citations from reliable sources. Unrelated material can be challenged and removed.
Find Sources: "Combination Reaction" - News · Newspapers · Books · Scholar · JSTOR (April 2009) (Learn how and when to remove this template message)

A combination reaction (also known as a synthesis reaction) is a reaction in which two or more elements or compounds (reactants) combine to form a single compound (product). Such reactions are represented by equations of the form: X + Y → XY. The combination of two or more elements to form a compound is called a combination reaction a) Between elements | C + O2 → CO2 | Carbon completely burned in oxygen gives carbon dioxide | - | b) Between links | CaO + H 2 O → Ca (OH) 2 | Calcium oxide (lime) in combination with water results in calcium hydroxide (slaked lime) | - | c) Between elements and compounds 2CO + O2 → 2CO2 | Oxygen combines with carbon monoxide and carbon dioxide is formed. |}

There is no specific number of reactants in a combination reaction.

Combination reactions are usually exothermic because the bond forms between the reactants and heat is released. For example, barium metal and fluorine gas combine in a highly exothermic reaction to form the salt barium fluoride:

Ba + F2 → BaF2

Another example is the combination of magnesium oxide with carbon dioxide to produce magnesium carbonate.

MgO + CO2 → MgCO3

Another example is the combination of iron with sulfur to produce iron (II) sulfide.

Fe + S → FeS

When a combination reaction occurs between a metal and a non-metal, the product is an ionic solid. An example could be lithium, which reacts with sulfur to form lithium sulfide. When magnesium burns in air, the atoms of the metal combine with the gas oxygen to form magnesium oxide. This specific combination reaction creates the bright flame produced by torches.

Combination reactions can also occur in other situations when the two products do not have the same ionic charge. In such a situation, different amounts of each reactant must be used. To put this in a chemical equation, a coefficient is added to one or more of the reactants so that the total ionic charge of each reactant is the same. For example, ferric oxide is formed by the following equation: 4 Fe + 3 O 2 ≤ 2 Fe 2 O 3 {\ displaystyle {\ ce {4Fe + 3 O2 -> 2Fe2O3}}} . This is because in this case iron has a charge of 3+, while every oxygen atom in O 2 {\ displaystyle {\ ce {O2}}} has a charge of 2-. Instead of elemental oxygen (O {\ displaystyle {\ ce {O}}} uss oxygen gas (O 2 {\ displaystyle {\ ce {O2}}} ) div id = "d6357a7024">

), because elemental oxygen is a free radical that is unstable and combines with other oxygen atoms to form O 2 {\ displaystyle {\ ce {O2}}} .

This chemical reaction article is a stub. You can help Wikipedia by expanding it.