DIVE Chemistry Quarterly Exam 3 Practice 2026 - Free Practice Questions and Study Guide

To determine the change in Gibbs free energy (ΔG°) for the combustion of propane (C3H8) in oxygen (O2), we start by considering the overall reaction:

\[ \text{C}_3\text{H}_8 + 5 \text{O}_2 \rightarrow 3 \text{CO}_2 + 4 \text{H}_2\text{O} \]

This reaction typically releases energy, indicating that the products are lower in energy than the reactants. Therefore, we expect ΔG° to be negative, which aligns with the high release of energy during combustion processes.

The calculated value of -495.9 kJ reflects the fact that combustion reactions are typically highly exothermic. The negative sign indicates that the process generates useful work or energy, making the reaction thermodynamically favorable. For many hydrocarbons, including propane, combustion leads to stable products (carbon dioxide and water) that have lower free energy compared to the original reactants.

Hence, the ΔG° value of -495.9 kJ indicates a strong driving force for this reaction, supporting the notion that propane combustion is spontaneous under standard conditions. Thus, this choice accurately represents the energetic dynamics of