Which of the following is the correctly balanced chemical equation for the combustion of propane (C_3H_8)?

• A. C_3H_8 + 5 O_2 → 3 CO_2 + 4 H_2O
• B. C_3H_8 + 3 O_2 → 3 CO_2 + 4 H_2O
• C. C_3H_8 + 4 O_2 → 3 CO_2 + 4 H_2O
• D. C_3H_8 + 5 O_2 → 2 CO_2 + 4 H_2O

Answer: (A)

Verified step by step guidance

1. Write the unbalanced chemical equation for the combustion of propane: \(\mathrm{C_3H_8 + O_2 \rightarrow CO_2 + H_2O}\).
2. Balance the carbon atoms first. Since propane has 3 carbon atoms, place a coefficient of 3 in front of \(\mathrm{CO_2}\): \(\mathrm{C_3H_8 + O_2 \rightarrow 3 CO_2 + H_2O}\).
3. Balance the hydrogen atoms next. Propane has 8 hydrogen atoms, so place a coefficient of 4 in front of \(\mathrm{H_2O}\) because each water molecule has 2 hydrogens: \(\mathrm{C_3H_8 + O_2 \rightarrow 3 CO_2 + 4 H_2O}\).
4. Balance the oxygen atoms last. On the right side, there are \$3 \times 2 = 6\( oxygen atoms from \)\mathrm{CO_2}\( and \)4 \times 1 = 4\( oxygen atoms from \)\mathrm{H_2O}\(, totaling 10 oxygen atoms. Since oxygen gas is \)\mathrm{O_2}\(, divide 10 by 2 to get 5 molecules of \)\mathrm{O_2}\(: \)\mathrm{C_3H_8 + 5 O_2 \rightarrow 3 CO_2 + 4 H_2O}$.
5. Verify that all atoms are balanced on both sides: 3 carbons, 8 hydrogens, and 10 oxygens. This confirms the balanced equation.