The conversion of ozone into oxygen is exothermic under what conditions is ozone is most stable?
`2O_(3)(g)hArr3O_(2)(g)`

Options

A. At low pressure and low temperature
B. At high pressure and high temperature
C. At high pressure and low temperature
D. At low pressure and high temperature

Answer

To determine the conditions under which ozone (O₃) is most stable, we need to analyze the given reaction and apply the principles of chemical equilibrium, particularly focusing on exothermic reactions.

### Step-by-Step Solution:

1. **Identify the Reaction**:
The reaction given is:
\[ 2O_3(g) \rightleftharpoons 3O_2(g) \]
This indicates that two moles of ozone gas convert into three moles of oxygen gas.

2. **Determine the Nature of the Reaction**:
It is stated that the conversion of ozone to oxygen is exothermic. This means that the change in enthalpy (ΔH) for the reaction is negative:
\[ ΔH < 0 \]

3. **Understand the Effect of Temperature**:
For exothermic reactions, increasing the temperature shifts the equilibrium position to favor the endothermic direction (the reverse reaction in this case). Therefore, if we increase the temperature, the reaction will shift to the left, producing more ozone (O₃).
- **Conclusion**: Ozone is more stable at **high temperatures** because the equilibrium shifts to favor its formation.

4. **Understand the Effect of Pressure**:
According to Le Chatelier's principle, if the pressure is increased, the equilibrium will shift towards the side with fewer moles of gas. In this reaction:
- Reactants: 2 moles of O₃
- Products: 3 moles of O₂
Since there are fewer moles of gas on the reactant side (2 moles of O₃ vs. 3 moles of O₂), increasing the pressure will shift the equilibrium to the left, favoring the formation of ozone.
- **Conclusion**: Ozone is more stable at **high pressures** because the equilibrium shifts to favor its formation.

5. **Final Conclusion**:
Combining both effects, we find that ozone (O₃) is most stable under conditions of **high temperature and high pressure**.

### Answer:
Ozone is most stable at **high temperature and high pressure**.

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