What are produced when ethanol burns completely in air?

• A. Carbon monoxide and water
• B. Carbon dioxide and water
• C. Carbon dioxide only
• D. Carbon monoxide only

Answer: (B)

Complete combustion of ethanol in adequate oxygen fully oxidizes both carbon and hydrogen, giving carbon dioxide and water as products. Ethanol has the formula C2H5OH, and the balanced equation for its complete combustion is C2H5OH + 3 O2 → 2 CO2 + 3 H2O. Because all carbon becomes CO2 and all hydrogen becomes H2O, these are the products you’d expect when ethanol burns cleanly in air. If oxygen were limited, incomplete combustion could occur, producing carbon monoxide or other carbon-rich products, but with complete combustion the result is carbon dioxide and water.