Complete combustion is accomplished when?

Complete combustion of methane, a common hydrocarbon fuel, occurs when it reacts with the optimal amount of oxygen to produce only carbon dioxide and water as byproducts. The chemical equation for this reaction is:

[ \text{CH}_4 + 2 \text{O}_2 \rightarrow \text{CO}_2 + 2 \text{H}_2\text{O} ]

In this equation, one molecule of methane (CH4) reacts with two molecules of oxygen (O2). This ratio is essential because it ensures that all of the methane is burned completely. When exactly one part of methane is combined with two parts of oxygen, all carbon and hydrogen atoms in the methane can react, leading to an efficient energy release and minimal emission of carbon monoxide or unburned hydrocarbons.

The other options do not provide the correct stoichiometric ratio for complete combustion. For instance, one part methane and one part oxygen is insufficient and results in incomplete combustion, leading to carbon monoxide production. Similarly, one part methane with three parts oxygen is more than necessary, which may not guarantee complete combustion effectively and can waste fuel. Finally, two parts methane with one part oxygen is not a valid ratio as it does not fulfill the requirement for