How to Determine the Balanced Chemical Equation for the Reaction of C8H18 and O2?

To balance the combustion reaction of octane (C₈H₁₈) with oxygen (O₂), we follow these steps:

Start with the unbalanced equation:
```
C₈H₁₈ + O₂ → CO₂ + H₂O
```
Count the number of atoms for each element in the reactants and products. In C₈H₁₈, there are 8 carbon (C) atoms and 18 hydrogen (H) atoms. For the products, carbon dioxide (CO₂) will contribute 1 carbon atom per molecule, and water (H₂O) will contribute 2 hydrogen atoms per molecule.
Balance the carbon atoms first. Place a coefficient of 8 in front of CO₂:
```
C₈H₁₈ + O₂ → 8CO₂ + H₂O
```
Next, balance the hydrogen atoms. Since there are 18 hydrogen atoms in C₈H₁₈, you will need 9 water molecules:
```
C₈H₁₈ + O₂ → 8CO₂ + 9H₂O
```
Now count the total number of oxygen atoms in the products. From 8CO₂, you get 16 oxygen atoms, and from 9H₂O, you get 9 more. This gives a total of 25 oxygen atoms:
```
8 * 2 (from CO₂) + 9 * 1 (from H₂O) = 25
```
To balance the oxygen in the reactants, remember each O₂ provides 2 oxygen atoms. Therefore, you need 12.5 O₂ molecules. However, we cannot have a fraction in our final coefficients, so we double all coefficients to get whole numbers:
```
2C₈H₁₈ + 25O₂ → 16CO₂ + 18H₂O
```

Thus, the balanced equation is:

2C₈H₁₈ + 25O₂ → 16CO₂ + 18H₂O

The coefficients are: 2, 25, 16, 18.

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