G2 Gas Fitter Practice Exam

Which gas is not typically a byproduct of complete natural gas combustion?

1. Carbon dioxide

2. Water vapor

3. Nitrogen

4. Carbon monoxide

The correct answer is: Carbon monoxide

Complete combustion of natural gas, which primarily consists of methane (CH4), ideally produces carbon dioxide and water vapor as the primary byproducts. In this reaction, the carbon atoms from methane combine with oxygen to create carbon dioxide, while the hydrogen atoms combine with oxygen to form water vapor. Therefore, carbon dioxide and water vapor are standard products of complete combustion. Nitrogen, while present in the air, is not a byproduct of the combustion process itself. It remains largely unchanged during combustion and does not react significantly under typical conditions where natural gas is burned. Instead, it simply exists in the environment during the combustion process. Carbon monoxide, on the other hand, is commonly produced during incomplete combustion when there is insufficient oxygen available for the carbon in the fuel to oxidize fully to carbon dioxide. This is indicative of a less efficient burning process, representing a less complete reaction compared to the ideal combustion scenario. Thus, when evaluating the byproducts of complete natural gas combustion, nitrogen is not a product that is formed through the chemical reaction of burning the fuel, and it distinguishes itself from the other gases listed since they arise directly as a result of the combustion process.