Which type of reaction involves exchange of components between two reactants to form new substances?

• A. Addition reactions
• B. Decomposition
• C. Combustion reactions
• D. Metathesis (displacement) reactions

Answer: (D)

Exchange of components between two reactants to form new substances is the hallmark of metathesis, or double-displacement, reactions. In this type, the partners in the two compounds swap places to yield two new compounds, typically written as AB + CD → AD + CB. This captures the idea of exchanging partners to create different substances, such as when a salt metathesis forms a precipitate or an acid–base reaction produces water and a salt.

Other reaction types don’t involve this kind of partner exchange. Addition reactions merge two species into one, decomposition breaks one substance into simpler pieces, and combustion involves a fuel reacting with oxygen to form oxides like CO2 and H2O through oxidation-reduction. Hence, the described process fits metathesis best.