Answer:
C₃H₈ + 5 O₂ ⇒ 3 CO₂ + 4 H₂O
2 C₃H₈ + 10 O₂ ⇒ 6 CO₂ + 8 H₂O
Explanation:
The combustion reaction is when propane reacts to oxygen to form a compound of carbon and water. If the product of carbon is carbon dioxide, the combustion is called complete. Let's considered the unbalanced combustion reaction.
(Note: I assume is C₃H₈, propane, because C₃H₁₈ doesn´t exist).
C₃H₈ + O₂ ⇒ CO₂ + H₂O
We will start balancing C and H that are just in 1 compound on each side, and finally we will balance O atoms. One way to do so is:
C₃H₈ + 5 O₂ ⇒ 3 CO₂ + 4 H₂O
We can get a different way of balancing the equation if we, for instance, multiply all the stoichiometric coefficients by 2.
2 C₃H₈ + 10 O₂ ⇒ 6 CO₂ + 8 H₂O
