Question

Propane (C \(_{3} \mathrm{H}_{8}\) ) reacts with elemental oxygen gas to produce carbon dioxide while giving off \(2,220 \mathrm{~kJ}\) of energy. Is this process endothermic or exothermic?

Short answer

The process is exothermic.

Step-by-step solution

Identify the Reaction

The reaction between propane (\(C_3H_8\)) and oxygen (\(O_2\)) can be written as: \[ C_3H_8 + 5O_2 \rightarrow 3CO_2 + 4H_2O \] This is a combustion reaction where propane reacts with oxygen to produce carbon dioxide (\(CO_2\)) and water (\(H_2O\)).

Analyze the Energy Change

The problem statement mentions that the reaction gives off \(2,220 \text{ kJ}\) of energy. When a reaction releases energy to its surroundings, it is known as an exothermic reaction.

Determine if the Process is Endothermic or Exothermic

In an exothermic process, energy is released (as opposed to absorbed in endothermic processes), resulting in negative enthalpy change. Since the reaction releases energy, it is exothermic.

Key concepts

Combustion Reaction

A combustion reaction is a chemical process where a substance reacts rapidly with oxygen, releasing energy in the form of heat and light. This kind of reaction is crucial in understanding fire and its applications like in engines and heating systems. Combustion reactions are characterized by \(O_2\) as a reactant and typically produce \(CO_2\) and \(H_2O\) as by-products.

Key characteristics of combustion reactions include:

• **Rapid energy release**: Often results in flames.
• **Common reactants and products**: Typically involve hydrocarbons and yield carbon dioxide and water.
• **Exothermic nature**: Energy is released, warming the surroundings.

Combustion is a fundamental reaction that helps power vehicles, generate electricity, and heat homes, making it a vital part of everyday life.

Propane Combustion

Propane combustion specifically refers to the chemical reaction where propane \((C_3H_8)\) reacts with oxygen \((O_2)\) to produce carbon dioxide \((CO_2)\), water \((H_2O)\), and energy. This process is not only a textbook example of a combustion reaction but also practical, as propane is a commonly used fuel.

The balanced chemical equation for this reaction is:
\[ C_3H_8 + 5O_2 \rightarrow 3CO_2 + 4H_2O \]

During propane combustion:

• Propane and oxygen react in a precise stoichiometric ratio.
• Energy is released, making it an efficient fuel source.
• Complete combustion leads to cleaner products like \(CO_2\) and \(H_2O\), but incomplete combustion can result in carbon monoxide \((CO)\), which is hazardous.

Propane's efficient combustion properties make it a popular choice for energy in various applications, from home heating to grilling.

Energy Release in Chemical Reactions

Understanding energy release in chemical reactions is key to grasping how substances transform during these processes. Energy in chemical reactions can either be absorbed or released, leading to two types of reactions: exothermic and endothermic.

Important points about energy release include:

• **Exothermic reactions**: Release energy, typically as heat, making the surroundings warmer. They have a negative enthalpy change \((\Delta H < 0)\).
• **Endothermic reactions**: Absorb energy, resulting in a temperature decrease of the surroundings, and have a positive enthalpy change \((\Delta H > 0)\).

The reaction of propane combustion is a classic example of an exothermic reaction. It releases a significant amount of energy, \(2,220 \text{ kJ}\), which can be harnessed for various practical applications. This release of energy is what powers many aspects of modern life, utilizing chemical reactions for heating, transportation, and electricity generation.