Question

A common means of forming small quantities of oxygen gas in the laboratory used to be to heat KClO₃(s): 2KClO₃(s) → 2KCl(s) + 3O₂(g) ΔH° = -89.4 kJ. Is this reaction endothermic or exothermic?

1) Endothermic
2) Exothermic

Answer 1

The reaction of heating KClO₃ to form KCl and O₂ is exothermic since the enthalpy change is -89.4 kJ, indicating that energy is released to the surroundings.

Step-by-step explanation:

The reaction of heating potassium chlorate (KClO₃) to form potassium chloride (KCl) and oxygen gas (O₂) is represented by the equation 2KClO₃(s) → 2KCl(s) + 3O₂(g). Given the enthalpy change (ΔH°) is -89.4 kJ for the reaction, this indicates that energy is released during the reaction process.

An exothermic reaction is one where energy, usually in the form of heat, is released to the surroundings. In contrast, an endothermic reaction absorbs energy from the surroundings. Since the enthalpy change is negative, it is clear that this reaction is exothermic, as it releases heat into the surrounding environment.