Question

Write an definition and example for combination reaction and decomposition reaction.

Answer 1

Answer:

Explanation:

A composition reaction (sometimes also called a combination reaction or a synthesis 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)

Answer 2

Combination reaction : when two or more reactants combine to form a single product, it is known as combination reaction.

Eg : CaO + H2O — Ca(OH)2

Decomposition reaction : when a single reactant breaks down to form two or more products, the it is known as decomposition reaction.

Eg : Pb(NO3)2 — PbO + NO2 + O2