When decane undergoes complete combustion, a mixture of carbon dioxide and water is formed - Edexcel - GCSE Chemistry - Question 4 - 2016 - Paper 1

To balance the combustion reaction of decane, we start with the reaction:

$2C_{10}H_{22} + O_2 → CO_2 + H_2O$

1. Count Carbon Atoms: There are 20 carbon atoms in 2C₁₀H₂₂, which means we need 20 CO₂ produced.

   $CO_2 = 20$

2. Count Hydrogen Atoms: There are 44 hydrogen atoms in 2C₁₀H₂₂, which means we need 22 H₂O produced.

   $H_2O = 22$

3. Balance Oxygen Atoms: The total oxygen from the products is:

   $20 CO_2 imes 2 = 40 ext{ O}$ $22 H_2O imes 1 = 22 ext{ O}$

Total Oxygen needed = 40 + 22 = 62 oxygen atoms, which means:

$$rac{62}{2} = 31 O_2$$

Thus, the complete balanced equation is:

$2C_{10}H_{22} + 31O_2 → 20CO_2 + 22H_2O$