Which reaction type describes a hydrocarbon reacting with oxygen to form carbon dioxide and water?

• A. Synthesis
• B. Decomposition
• C. Single-Replacement
• D. Combustion

Answer: (D)

This is combustion. When a hydrocarbon (a fuel made of hydrogen and carbon) reacts with oxygen, it typically releases energy and forms carbon dioxide and water. For complete combustion, the main products are CO2 and H2O, as in the general equation hydrocarbon + O2 → CO2 + H2O. This distinguishes it from other reaction types: synthesis builds a more complex substance from simpler ones, decomposition breaks one substance into simpler pieces, and single-replacement swaps elements in compounds. In combustion, the hydrocarbon and oxygen are simply consumed to produce the oxides of carbon and hydrogen rather than forming a single new compound or breaking a compound apart.