<em><u>Decomposition reactions are types of reaction that occurs when a reactant is broken down into two or more products. </u></em>
Decomposition may either be thermal where heat is used to break a reactant or may be catalytic where a catalyst is used to break down a reactant to yield two or more substance, for example decomposition of hydrogen peroxide.
<em><u>All metal carbonates decompose to produce a metal oxide and carbon dioxide gas.</u></em>
<em><u>Calcium carbonate undergoes thermal decomposition to form calcium oxide and carbon dioxide. </u></em>
The equation will be;
CaCO3(s) → CaO(s) + CO2(g)
The equation is balanced as the number of atoms of each element are equal on both side.