Decomosition reaction is single compound break into two or more simple substances under suitable conditions.
calcium carbonate is decomose by heating and form calcium oxide and carbon dioxide
CaCO3 --> CaO + CO2
displacement reaction in which a more reactive element displaces a less reactive element.
zinc react with hydrochloric acid and zinc displace the hydrogen and produce zinc chloride and hydrogen gas.
Zn + 2HCl --> ZnCl₂ + H₂