What is the balanced equation for the complete combustion of methane?

What is the balanced equation for the complete combustion of methane?

• A. CH4 + O2 → CO2 + 2 H2O
• B. CH4 + 2 O2 → CO2 + 2 H2O
• C. CH4 + 3 O2 → CO2 + 4 H2O
• D. CH4 + O2 → CO2 + H2O

Answer: (B)

Balancing a combustion equation means keeping the number of each type of atom the same on both sides. For methane, the complete combustion products are carbon dioxide and water, so you’ll expect one CO2 and some H2O. Methane has one carbon and four hydrogens, so the products must have one CO2 and two H2O to conserve C and H. That gives CH4 + ? O2 → CO2 + 2 H2O. Now count oxygen on the right: CO2 has 2 O and 2 H2O has 2 O, for a total of 4 O. To supply four oxygens, you need two O2 molecules (each O2 has 2 O). So the balanced equation is CH4 + 2 O2 → CO2 + 2 H2O. Other patterns, like CH4 + 3 O2 → CO2 + 4 H2O, use more oxygen and aren’t the simplest whole-number balance, even though they also conserve atoms. The standard balanced form uses the smallest whole-number coefficients.

Balancing a combustion equation means keeping the number of each type of atom the same on both sides. For methane, the complete combustion products are carbon dioxide and water, so you’ll expect one CO2 and some H2O. Methane has one carbon and four hydrogens, so the products must have one CO2 and two H2O to conserve C and H. That gives CH4 + ? O2 → CO2 + 2 H2O. Now count oxygen on the right: CO2 has 2 O and 2 H2O has 2 O, for a total of 4 O. To supply four oxygens, you need two O2 molecules (each O2 has 2 O). So the balanced equation is CH4 + 2 O2 → CO2 + 2 H2O. Other patterns, like CH4 + 3 O2 → CO2 + 4 H2O, use more oxygen and aren’t the simplest whole-number balance, even though they also conserve atoms. The standard balanced form uses the smallest whole-number coefficients.