IB Chemistry R1.3.2 Incomplete Combustion Notes

Incomplete Combustion of Organic Compounds

What Is Incomplete Combustion?

1. As discussed in the previous section, combustion is a chemical reaction where a fuel reacts with oxygen, releasing energy in the form of heat or light.
2. In an ideal scenario, known as complete combustion, hydrocarbons (organic compounds made of carbon and hydrogen) burn in the presence of sufficient oxygen to produce carbon dioxide $CO_2$ and water $H_2O$.
3. However, when oxygen is in short supply, incomplete combustion occurs.
4. Instead of forming only carbon dioxide and water, incomplete combustion produces harmful byproducts like carbon monoxide $CO$ and elemental carbon $C$, commonly observed as soot.

General Equations for Incomplete Combustion:

1. Formation of carbon monoxide, for example: $$2\text{CH}_4 + 3\text{O}_2 \rightarrow 2\text{CO} + 4\text{H}_2\text{O}$$
2. Formation of carbon (soot), for example: $$\text{CH}_4 + \text{O}_2 \rightarrow \text{C} + 2\text{H}_2\text{O}$$
3. Formation of carbon monoxide from ethanol, for example: $$\text{C}_2\text{H}_5\text{OH} + 2\text{O}_2 \rightarrow 2\text{CO} + 3\text{H}_2\text{O}$$
4. Formation of carbon (soot) from ethanol, for example: $$\text{C}_2\text{H}_5\text{OH} + \text{O}_2 \rightarrow 2\text{C} + 3\text{H}_2\text{O}$$

Why Does Incomplete Combustion Occur?

Incomplete combustion happens when oxygen becomes the limiting reactant in the reaction. Several factors can contribute to this:

1. Poor ventilation:
   1. In confined or poorly ventilated spaces, oxygen levels may drop below the threshold needed for complete combustion.
2. Fuel composition: