What type of reaction occurs when a compound is broken down into simpler substances?

• A. Synthesis reaction
• B. Decomposition reaction
• C. Single replacement reaction
• D. Double replacement reaction

Answer: (B)

When a compound is broken down into simpler substances, a decomposition reaction occurs. This type of reaction specifically involves the breaking of bonds in a compound, resulting in two or more products that are simpler, smaller molecules or elements.

For instance, when water (H2O) is electrolyzed, it breaks down into hydrogen gas (H2) and oxygen gas (O2). This process demonstrates how a single compound can yield multiple simpler substances through a decomposition process.

In contrast, synthesis reactions involve the combination of two or more reactants to form a more complex product, while single and double replacement reactions involve the exchange of components between compounds rather than breaking them down. Therefore, the defining characteristic of a decomposition reaction is its role in reducing a compound to its fundamental parts, making it the correct choice in this context.