Combustion is the reaction with which element?

• A. Oxygen
• B. Hydrogen
• C. Nitrogen
• D. Carbon Dioxide

Answer: (A)

Combustion is rapid oxidation—the substance reacts with oxygen from the air to release heat (and often light) and form oxides. Because it’s the oxygen that acts as the oxidizing agent, this is the element involved in combustion. For example, burning a hydrocarbon in oxygen produces carbon dioxide and water. Hydrogen can burn in oxygen, but the key player driving the process is the oxygen itself, not hydrogen. Nitrogen is largely inert in ordinary combustion, and carbon dioxide is typically a product of complete combustion, not the reactant. So the element the reaction occurs with is oxygen.