What are the by-products of ethanol combustion in engines?

The by-products of ethanol combustion in engines are carbon dioxide (CO2), water (H2O), and heat energy.

When ethanol (C2H5OH) is used as a fuel in engines, it undergoes a combustion reaction. This is a type of exothermic reaction, meaning it releases heat energy. The ethanol reacts with oxygen (O2) in the air to produce carbon dioxide and water. This reaction can be represented by the following balanced chemical equation:

C2H5OH(l) + 3O2(g) → 2CO2(g) + 3H2O(l) + heat energy

The carbon dioxide and water produced are expelled from the engine as exhaust gases. The heat energy released is used to power the engine.

It's important to note that while carbon dioxide is a greenhouse gas that contributes to global warming, ethanol is considered a renewable fuel because it's typically produced from plant materials. These plants absorb carbon dioxide from the atmosphere as they grow, which can offset some of the emissions from burning the fuel. However, the overall environmental impact of ethanol fuel depends on various factors, including how the plants are grown and how the fuel is produced and transported.

In addition to carbon dioxide and water, incomplete combustion of ethanol can also produce carbon monoxide (CO) and particulate matter. Incomplete combustion occurs when there isn't enough oxygen to fully oxidise the fuel. This can happen in real-world engines, especially under certain operating conditions. Carbon monoxide is a poisonous gas, and particulate matter can contribute to air pollution and health problems. Therefore, it's important for engines to be designed and maintained to minimise incomplete combustion.