AIIMS 2005 Chemistry Ozone Assertion Reason Question

To tackle this question, we need to analyze both the assertion and the reason carefully.

Assertion Analysis

Assertion: Ozone is a powerful oxidising agent in comparison to O₂.

Ozone (O₃) is indeed a more potent oxidizing agent than molecular oxygen (O₂). This is primarily due to its molecular structure and the presence of a higher energy level of the central oxygen atom in ozone. The reaction of ozone with various substances often results in the gain of electrons (reduction) for the ozone molecule, making it an effective oxidizer. The standard electrode potential for the reduction of ozone to oxygen is higher than that for the reduction of oxygen, which indicates that ozone can oxidize other substances more readily than oxygen can.

Reason Analysis

Reason: Ozone is diamagnetic but O₂ is paramagnetic.

This statement is true. Ozone (O₃) has all paired electrons in its molecular orbitals, which makes it diamagnetic. In contrast, molecular oxygen (O₂) has two unpaired electrons in its π* antibonding molecular orbitals, rendering it paramagnetic. However, while this distinction between diamagnetism and paramagnetism is accurate, it does not directly explain why ozone is a stronger oxidizing agent than oxygen. Thus, the reason does not serve as a correct explanation for the assertion.

Conclusion

Correct Answer: B) If both assertion and reason are true but reason is not the correct explanation of assertion.

Explanation of Incorrect Options

• Option A: Incorrect because, while both the assertion and reason are true, the reason does not provide the correct explanation for the assertion.
• Option C: Incorrect because the assertion is true (ozone is a stronger oxidizing agent) while the reason is also true (ozone is diamagnetic and O₂ is paramagnetic).
• Option D: Incorrect as both the assertion and reason are true; hence, this option cannot be valid.

Summary

Thus, both the assertion and the reason are true statements, but the reason does not elucidate why ozone is a better oxidizing agent. Therefore, the correct answer is B. Understanding the oxidative properties of ozone compared to oxygen involves looking at their molecular structures and the resulting electron configurations, rather than merely their magnetic properties.