Final answer:
A single-replacement reaction involves one element substituting for another in a compound, producing a new element and a new compound. These reactions are redox reactions that can involve metals or nonmetals. In contrast, a decomposition reaction involves a single compound breaking down into two or more substances.
Step-by-step explanation:
A single-replacement reaction is a type of chemical reaction characterized by one element being substituted for another element within a compound, leading to the formation of a new element and a new compound. An example of this is the reaction 2 HCl(aq) + Zn(s) → ZnCl₂ (aq) + H₂(g), where zinc (Zn) replaces the hydrogen (H) in hydrochloric acid (HCl) to form zinc chloride (ZnCl₂) and hydrogen gas (H₂). Single-replacement reactions can involve either metals or nonmetals. These reactions are also considered redox reactions, where the displacement occurs through the process of oxidation of a metallic element.
On the other hand, a decomposition reaction involves the breakdown of a single compound into two or more substances. This could result in the formation of elements, compounds, or a combination of both. An example is the decomposition of water into hydrogen and oxygen gases.
Given these definitions, if the reaction in question produced multiple substances from a single compound, it would be a decomposition reaction. Conversely, if the reaction in question involved an element replacing another within a compound, it would be a single-replacement reaction.