Answer
$2C_{3}H_{6}(g)+9O_{2}(g)\rightarrow 6CO_{2}(g)+6H_{2}O(g)$
Work Step by Step
Complete combustion of alkenes produces carbon dioxide and water. Therefore, we can write
$C_{3}H_{6}(g)+O_{2}(g)\rightarrow CO_{2}(g)+H_{2}O(g)$
Now, we try to balance the number of H, C and O atoms in the left and right side.
Step 1: Balancing C atoms
$C_{3}H_{6}(g)+O_{2}(g)\rightarrow 3CO_{2}(g)+H_{2}O(g)$
Step 2: Balancing H atoms
$C_{3}H_{6}(g)+O_{2}(g)\rightarrow 3CO_{2}(g)+3H_{2}O(g)$
Step 3: Balancing O atoms
$C_{3}H_{6}(g)+\frac{9}{2}O_{2}(g)\rightarrow 3CO_{2}(g)+3H_{2}O(g)$
Step 4: Converting stoichiometric coefficient of $O_{2}$ into integer
$2C_{3}H_{6}(g)+9O_{2}(g)\rightarrow 6CO_{2}(g)+6H_{2}O(g)$
We find that the equation is balanced in the above step.
