What characterizes a combustion reaction?

• A. A reaction where an acid and base form water
• B. A compound decomposes
• C. One element replaces another
• D. A hydrocarbon reacts with oxygen to form carbon dioxide and water

Answer: (D)

Combustion is a reaction where a fuel reacts with an oxidizer, usually oxygen, releasing energy and forming oxides of the elements involved. For hydrocarbons, the classic combustion product is carbon dioxide and water, especially in complete combustion.

That description matches a hydrocarbon reacting with oxygen to form carbon dioxide and water, which is the defining feature of a combustion process.

The other scenarios describe different types of reactions: acid-base neutralization forms water and a salt but not through oxidation with oxygen; decomposition breaks a single compound into simpler substances; and a single-replacement reaction swaps elements but does not involve burning with oxygen to produce CO2 and H2O.