What describes a decomposition reaction?

• A. A reaction where one element replaces another
• B. A reaction where a compound breaks into simpler products
• C. A hydrocarbon reacts with oxygen to form CO2 and H2O
• D. A reaction with acid and base forming water

Answer: (B)

A decomposition reaction is when a single compound breaks apart into two or more simpler substances. This is the opposite of synthesis, and it often requires energy input (like heat, light, or electricity) to break the chemical bonds.

In the options given, the description that a compound breaks into simpler products fits this idea exactly. For example, heating calcium carbonate to form calcium oxide and carbon dioxide, or the breakdown of hydrogen peroxide into water and oxygen, are classic decomposition processes.

The other descriptions describe different types of reactions: one describes a displacement reaction where an element replaces another; another describes combustion, where a hydrocarbon reacts with oxygen to produce CO2 and H2O; and another describes neutralization, where an acid and base form water.