Michigan Test for Teacher Certification (MTTC) Secondary Integrated Science Practice test

In which type of reaction does one element replace another in a compound?

1. Decomposition reaction

2. Single replacement reaction

3. Double replacement reaction

4. Composition reaction

The correct answer is: Single replacement reaction

The type of reaction in which one element replaces another in a compound is known as a single replacement reaction. In this process, an uncombined element reacts with a compound and displaces an element from it, resulting in the formation of a new compound and a different uncombined element. For example, if zinc is added to hydrochloric acid, zinc displaces hydrogen from the compound, forming zinc chloride and releasing hydrogen gas. This reaction exemplifies the fundamental principle of a single replacement reaction, where one element takes the place of another within a chemical compound. In contrast, a decomposition reaction involves the breakdown of a single compound into two or more simpler products, rather than involving the replacement of elements. A double replacement reaction involves the exchange of ions between two compounds, with no single element displacing another within a compound. A composition reaction, also known as a synthesis reaction, involves combining two or more elements or compounds to form a single compound. Each of these reactions follows distinct mechanisms that do not involve the direct replacement of one element for another in a compound, which is the hallmark of a single replacement reaction.