Question

Your family may have a "gas grill" for outdoor cooking. Gas grills typically use bottled propane gas \(\left(\mathrm{C}_{3} \mathrm{H}_{8}\right),\) which burns in air (oxygen) to produce carbon dioxide gas and water vapor. Write the unbalanced chemical equation for this process. Gas grills should never be used indoors, however, because if the supply of oxygen is restricted, the products of the reaction tend to be water vapor and toxic carbon monoxide, instead of nontoxic carbon dioxide. Write the unbalanced chemical equation for this process.

Short answer

The unbalanced chemical equation for the complete combustion of propane is: \[\mathrm{C}_{3} \mathrm{H}_{8} + \mathrm{O}_{2} \rightarrow \mathrm{CO}_{2} + \mathrm{H}_{2}\mathrm{O}\] The unbalanced chemical equation for the incomplete combustion of propane is: \[\mathrm{C}_{3} \mathrm{H}_{8} + \mathrm{O}_{2} \rightarrow \mathrm{CO} + \mathrm{H}_{2}\mathrm{O}\]

Step-by-step solution

Write the unbalanced equation for complete combustion of propane

In this process, propane \(\left(\mathrm{C}_{3} \mathrm{H}_{8}\right)\) reacts with oxygen \(\left(\mathrm{O}_{2}\right)\) to produce carbon dioxide \(\left(\mathrm{CO}_{2}\right)\) and water vapor \(\left(\mathrm{H}_{2}\mathrm{O}\right)\). The unbalanced chemical equation for this process is: \[\mathrm{C}_{3} \mathrm{H}_{8} + \mathrm{O}_{2} \rightarrow \mathrm{CO}_{2} + \mathrm{H}_{2}\mathrm{O}\]

Write the unbalanced equation for incomplete combustion of propane

In this process, propane \(\left(\mathrm{C}_{3} \mathrm{H}_{8}\right)\) reacts with a limited supply of oxygen \(\left(\mathrm{O}_{2}\right)\) to produce toxic carbon monoxide \(\left(\mathrm{CO}\right)\) and water vapor \(\left(\mathrm{H}_{2}\mathrm{O}\right)\). The unbalanced chemical equation for this process is: \[\mathrm{C}_{3} \mathrm{H}_{8} + \mathrm{O}_{2} \rightarrow \mathrm{CO} + \mathrm{H}_{2}\mathrm{O}\]

Key concepts

Chemical Equations

A chemical equation is a symbolic representation of a chemical reaction. It shows reactants transforming into products. These equations help us understand what happens during a reaction. Each molecule or compound in the reaction is represented by its chemical formula. For example, in the reaction of propane burning, propane is represented as \( \mathrm{C}_{3} \mathrm{H}_{8} \), and oxygen is \( \mathrm{O}_{2} \).
\( \rightarrow \) marks the transformation from reactants (on the left) to products (on the right). The equation must accurately reflect the conservation of mass. This means that atoms on both sides of the equation should be equal. When balancing equations, we use coefficients to equalize the number of atoms involved for each element.

Unbalanced equations simply show the chemical process, like those in our exercise for both complete and incomplete combustion. However, remember that balancing them is crucial to truly represent the physical reality of the reaction and uphold the laws of chemistry.

Propane Combustion

Propane combustion is the process of burning propane in oxygen to produce heat and light. Propane, with a chemical formula \( \mathrm{C}_{3} \mathrm{H}_{8} \), is a common fuel used for grills. During combustion, chemical bonds are broken and new ones are formed, releasing energy in the form of heat.
When propane is combusted completely, it reacts with oxygen to produce carbon dioxide \( \mathrm{CO}_{2} \) and water vapor \( \mathrm{H}_{2}\mathrm{O} \). This complete combustion is more efficient and produces less harmful emissions. The reaction can be represented as an unbalanced chemical equation:

• Reactants: Propane \( (\mathrm{C}_{3} \mathrm{H}_{8}) \) and Oxygen \( (\mathrm{O}_{2}) \)
• Products: Carbon Dioxide \( (\mathrm{CO}_{2}) \) and Water \( (\mathrm{H}_{2}\mathrm{O}) \)

Complete combustion requires enough oxygen for all carbon atoms to form \( \mathrm{CO}_{2} \). Ensuring ample airflow when using propane can help achieve complete combustion.

Complete vs Incomplete Combustion

Complete and incomplete combustion of hydrocarbons like propane depend on the supply of oxygen. Complete combustion implies a sufficient oxygen supply, leading to cleaner emissions. Incomplete combustion occurs when oxygen is lacking.
During complete combustion, all carbon in the fuel converts into carbon dioxide \( \mathrm{CO}_{2} \). This process is efficient and less polluting, generating maximum energy. However, If the oxygen supply is restricted, incomplete combustion takes place. Here, carbon is partially oxidized, creating carbon monoxide \( \mathrm{CO} \) instead of carbon dioxide.

Both forms of combustion produce water vapor \( \mathrm{H}_{2}\mathrm{O} \). But it is crucial to strive for complete combustion due to lower toxic by-product formation and greater energy efficiency. Understanding the difference helps in optimizing fuel usage and environmental safety.

Toxicity of Carbon Monoxide

Carbon monoxide \( (\mathrm{CO}) \) is a dangerous and toxic substance produced during incomplete combustion. It is a colorless, odorless gas, making it difficult to detect without proper equipment.
\( \mathrm{CO} \) poses numerous health risks. When inhaled, it binds with hemoglobin in the blood, restricting oxygen delivery to the body. Symptoms of exposure include headaches, dizziness, and at high concentrations, can be lethal.
Gas appliances and engines are potential sources of carbon monoxide, especially indoors where ventilation is limited. To prevent \( \mathrm{CO} \) buildup:

• Ensure proper ventilation when using gas-powered devices.
• Use carbon monoxide detectors to monitor air quality.
• Regularly maintain appliances to ensure they function correctly.

By understanding the risks and taking adequate precautions, we can manage the dangers associated with carbon monoxide effectively.