Combination reaction

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A combination reaction is a reaction where two reactants are combined into one product.Those reaction in which two or more elements or compounds combine together to form a single compound are called combination reaction. They may be represented by X + Y → XY Combination reactions are usually exothermic. For example barium metal and fluorine gas will combine in a highly exothermic reaction to form the salt barium fluoride:

                               Ba + F2BaF2 

Another example is magnesium oxide combining with carbon dioxide to produce magnesium carbonate.

                               MgO+ CO2MgCO3 

Another example is Iron combining with Sulphur to produce Iron(II) Sulfide.

                               Fe+ SFeS 

Often, reactions can fall into more than one category. For example the combustion of magnesium metal is also a combination reaction as it releases magnesium oxide and energy.

                                 2Mg+O22MgO + Heat 

This reaction is usually exothermic because when the bond forms between the reactants, heat is released.

A combination reaction can be of three types:

TypeExample
a) Between two elementsC + O2 → CO2Carbon completely burnt in oxygen yields carbon dioxide
b) Between two compounds2CaO + 2H2O → 2Ca(OH)2Calcium oxide (lime) combined with water gives calcium hydroxide (slaked lime)
c) Between one element and one compound2CO + O2 → 2CO2Oxygen combines with Carbon monoxide, Carbon dioxide is formed.

When a combination reaction occurs between a metal and a nonmetal the product is an ionic solid. An example could be lithium reacting with sulfur to give lithium sulfide. When magnesium burns in air, the atoms of the metal combine with the gas oxygen to produce magnesium oxide. This specific combination reaction produces the bright flame generated by flares. There is no specific number of products that can be formed in combination reaction.