Question

A combustion reaction involves the reaction of a substance with oxygen gas. The complete combustion of any hydrocarbon (binary compound of carbon any hydrogen produces carbon dioxide and water as the only products. Octane is a hydrocarbon found in gasoline. Complete combustion of octane produces 8L of carbon dioxide for every 9L of water vapor (both measured at the same temperature and pressure). What is the ratio of carbon atoms to hydrogen atoms in a molecule of octane?

Short answer

The ratio of carbon to hydrogen in the molecule of octane is$4:9$.

Step-by-step solution

Octane

The molecule octane has the molecular formula of ${\mathbf{C}}_{\mathbf{8}}{\mathbf{H}}_{\mathbf{18}}$. It is an example of hydrocarbon. On complete combustion, it forms ${\mathbf{CO}}_{\mathbf{2}}$and ${\mathbf{H}}_{\mathbf{2}}\mathbf{O}$.

Explanation

So the ratio of carbon atoms to hydrogen atoms in the octane molecule (${\text{C}}_{\text{8}}{\text{H}}_{\text{18}}$) is 4:9 and is shown below:

$$\begin{gathered} \text{C:O} \\ 8:18=4:9 \end{gathered}$$