Question

What is the difference between combination and decomposition reaction? Give one example of each type.

Answer 1

A composition reaction (sometimes also called a combination reaction or asynthesis reaction) produces a single substance from multiple reactants. A single substance as a product is the key characteristic of the composition reaction. There may be a coefficient other than one for the substance, but if the reaction has only a single substance as a product, it can be called a composition reaction. In the reaction

2 H2(g) + O2(g) → 2 H2O(ℓ)

water is produced from hydrogen and oxygen. Although there are two molecules of water being produced, there is only one substance—water—as a product. So this is a composition reaction.

A decomposition reaction starts from a single substance and produces more than one substance; that is, it decomposes. One substance as a reactant and more than one substance as the products is the key characteristic of a decomposition reaction. For example, in the decomposition of sodium hydrogen carbonate (also known as sodium bicarbonate),

2 NaHCO3(s) → Na2CO3(s) + CO2(g) + H2O(ℓ)

sodium carbonate, carbon dioxide, and water are produced from the single substance sodium hydrogen carbonate.

Answer 2

Combination reaction is a reaction in which two or more element combine to form a new compound. Ex- C+O2 ---Co2. In decomposition reaction a compound broken down to form two or more than two products. Ex - CaCo3 -∆-- Ca0 + Co2.