At one time, a common means of forming small quantities of oxygen gas in the laboratory was to heat KClO₃: 2 KClO₃(s) → 2 KCl(s) + 3 O₂(g) ΔH = -89.4 kJ (c) The decomposition of KClO₃ proceeds spontaneously when it is heated. Do you think that the reverse reaction, the formation of KClO₃ from KCl and O₂, is likely to be feasible under ordinary conditions? Explain your answer.

Verified step by step guidance

1. Identify the reaction type: The given reaction is a decomposition reaction where potassium chlorate (KClO3) breaks down into potassium chloride (KCl) and oxygen gas (O2) upon heating.
2. Analyze the reaction's enthalpy change (ΔH): The reaction has a negative ΔH value of -89.4 kJ, indicating that it is exothermic. This means that energy is released when KClO3 decomposes.
3. Consider the reverse reaction: The reverse reaction would be the synthesis of KClO3 from KCl and O2. Since the forward reaction is exothermic, the reverse reaction would be endothermic, requiring an input of energy (89.4 kJ).
4. Evaluate the feasibility under ordinary conditions: Endothermic reactions, such as the reverse reaction here, are generally not spontaneous at room temperature without an external source of energy.
5. Conclude based on spontaneity: Given that the reverse reaction is endothermic and would require continuous energy input to proceed, it is unlikely to be feasible under ordinary conditions without specific, controlled circumstances.

Key Concepts

Thermodynamics and Enthalpy

Thermodynamics is the study of energy transformations, and enthalpy (ΔH) is a key concept that measures the heat content of a system. In the given reaction, the negative ΔH indicates that the decomposition of KClO3 is exothermic, releasing energy. This suggests that the reverse reaction, which is endothermic, would require an input of energy to proceed, making it less favorable under ordinary conditions.

Spontaneity of Reactions

A reaction's spontaneity is determined by its Gibbs free energy change (ΔG), which considers both enthalpy and entropy. The decomposition of KClO3 is spontaneous at elevated temperatures, indicating that the products are favored. Conversely, the formation of KClO3 from KCl and O2 would likely have a positive ΔG under normal conditions, suggesting that it is not spontaneous and thus less feasible.

Reaction Conditions and Kinetics

The feasibility of a chemical reaction also depends on the conditions under which it occurs, including temperature, pressure, and concentration. The reverse reaction of forming KClO3 from KCl and O2 may require specific conditions, such as high temperatures or catalysts, to overcome the activation energy barrier. Without these conditions, the reaction is unlikely to proceed efficiently in a typical laboratory setting.