3rd Year Electrical Trades Qualification (TQ) Practice Exam 2026 – Your Complete All-in-One Study Guide for Exam Success!

When propane burns with enough oxygen, the reaction is complete and all the carbon becomes carbon dioxide while all the hydrogen becomes water. For propane, the balanced equation is C3H8 + 5 O2 → 3 CO2 + 4 H2O, so the main combustion products are carbon dioxide and water vapour.

This is why the answer is carbon dioxide and water vapour. The other substances listed would only appear as products under special or wrong conditions (for example, incomplete combustion can produce some carbon monoxide, but hydrogen gas is not a typical product of burning propane; oxygen and nitrogen are simply the gases in air, not combustion products; and methane is not formed from burning propane).