Which clue can be used to identify a chemical reaction as a combustion reaction?

• A. The reaction produces a color change without releasing heat.
• B. The reaction involves the exchange of ions between two compounds.
• C. The reaction results in the formation of a precipitate.
• D. The reaction involves a hydrocarbon reacting with O_2 to produce CO_2 and H_2O.

Answer: (D)

Verified step by step guidance

1. Understand that a combustion reaction typically involves a substance (usually a hydrocarbon) reacting with oxygen (O\_2).
2. Recognize that the key products of a combustion reaction are carbon dioxide (CO\_2) and water (H\_2O).
3. Note that combustion reactions release energy in the form of heat and sometimes light, which distinguishes them from other reaction types.
4. Identify that clues such as color change without heat, ion exchange, or precipitate formation do not specifically indicate combustion.
5. Conclude that the defining clue for a combustion reaction is the reaction of a hydrocarbon with O\_2 producing CO\_2 and H\_2O.