Which type of reaction involves the combination of two or more substances to form a single product?

The type of reaction that involves the combination of two or more substances to form a single product is known as a combination reaction. In this process, multiple reactants come together, and through a chemical reaction, they generate one product. This type of reaction can be represented generally by the formula A + B → AB, where A and B are reactants that combine to form the product AB.

Combination reactions are essential in various chemical processes, including the synthesis of compounds and materials. For instance, when hydrogen gas combines with oxygen gas, water is produced, exemplifying a combination reaction in practice.

The other types of reactions listed, such as decomposition, single-replacement, and double-replacement reactions, involve different mechanisms. Decomposition reactions break down a single compound into two or more products. Single-replacement reactions involve an element displacing another element in a compound, while double-replacement reactions involve the exchange of ions between two compounds. Each of these reactions has distinct characteristics that differentiate them from combination reactions.