Write the balanced equation for the complete combustion of ethanol (C2H5OH).

Write the balanced equation for the complete combustion of ethanol (C2H5OH).

• A. C2H5OH + 3 O2 → 2 CO2 + 3 H2O
• B. C2H5OH + O2 → CO2 + H2O
• C. C2H5OH + 4 O2 → 2 CO2 + 3 H2O
• D. C2H5OH + 2 O2 → CO2 + H2O

Answer: (A)

Balancing combustion means making sure the number of each type of atom is the same on both sides and using oxygen gas as the oxidizer, with carbon dioxide and water as the products. For ethanol, C2H5OH, there are 2 carbon atoms and 6 hydrogen atoms. That means the products must contain 2 CO2 molecules (one for each carbon) and 3 H2O molecules (to provide the six hydrogens). So the products are 2 CO2 and 3 H2O. Now check oxygen atoms: the right side has CO2 (2×2 = 4 O) plus H2O (3×1 = 3 O), totaling 7 O atoms. The ethanol molecule brings 1 O atom, so we need 6 more O atoms from O2, which is 3 O2 molecules. Putting it together gives C2H5OH + 3 O2 → 2 CO2 + 3 H2O. The other options don’t balance C, H, or O correctly, so they don’t conserve atoms.

Balancing combustion means making sure the number of each type of atom is the same on both sides and using oxygen gas as the oxidizer, with carbon dioxide and water as the products. For ethanol, C2H5OH, there are 2 carbon atoms and 6 hydrogen atoms. That means the products must contain 2 CO2 molecules (one for each carbon) and 3 H2O molecules (to provide the six hydrogens). So the products are 2 CO2 and 3 H2O.

Now check oxygen atoms: the right side has CO2 (2×2 = 4 O) plus H2O (3×1 = 3 O), totaling 7 O atoms. The ethanol molecule brings 1 O atom, so we need 6 more O atoms from O2, which is 3 O2 molecules. Putting it together gives C2H5OH + 3 O2 → 2 CO2 + 3 H2O. The other options don’t balance C, H, or O correctly, so they don’t conserve atoms.