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

What type of reaction involves the breaking down of a compound into two or more simpler substances?

1. Synthesis reaction

2. Decomposition reaction

3. Single replacement reaction

4. Double replacement reaction

The correct answer is: Decomposition reaction

The correct answer is a decomposition reaction, which is defined as a chemical reaction where a single compound breaks down into two or more simpler substances. This type of reaction typically requires energy input in the form of heat, light, or electricity to proceed. In a decomposition reaction, the molecular structure of the compound is altered, resulting in the formation of simpler substances, which can include elements or smaller compounds. A common example of a decomposition reaction is the breakdown of water (H2O) into hydrogen (H2) and oxygen (O2) gases through electrolysis. The other types of reactions listed—synthesis, single replacement, and double replacement—are defined differently. A synthesis reaction involves the combination of two or more simpler substances to form a more complex compound. Single replacement reactions occur when one element reacts with a compound, displacing another element within that compound. Double replacement reactions involve the exchange of ions between two compounds to form new products. Understanding these distinctions helps clarify the specific nature of decomposition reactions.