New York Low Pressure Boiler Certificate of Fitness (COF) Practice Test

What is recognized as the end product of complete combustion?

1. Carbon monoxide

2. Carbon dioxide

3. Water vapor

4. Ozone

The correct answer is: Carbon dioxide

The end product of complete combustion is carbon dioxide. Complete combustion occurs when a fuel burns in the presence of an adequate supply of oxygen, resulting in the most efficient conversion of the fuel's carbon content. During this process, carbon atoms from the fuel combine with oxygen molecules, forming carbon dioxide. In addition to carbon dioxide, water vapor is also produced, as hydrogen in the fuel reacts with oxygen, but the primary end product that signifies complete combustion is carbon dioxide. In the context of the other options, carbon monoxide is formed during incomplete combustion, where there is insufficient oxygen, leading to the production of less efficient and potentially harmful emissions. Water vapor is indeed a byproduct of combustion but is not recognized as the end product on its own. Ozone is a different molecule that is formed through atmospheric reactions involving sunlight, oxygen, and various pollutants, and is not a direct product of combustion at the level of gaseous fuels. Thus, while water vapor contributes to the combustion process, carbon dioxide is the definitive indicator of complete combustion in terms of gaseous emissions.