Concept:A species can act as both oxidising and reducing agent if its central element has an intermediate oxidation state; if it is at its maximum oxidation state, it can only be oxidised (i.e., act as an oxidising agent).
Explanation:• In
SO2​, sulphur has an oxidation state of
+4. It can be oxidised to
SO42−​ (S
+6) or reduced to S
0. Hence, it acts as both oxidising and reducing agent.
• In
H2​O2​, oxygen has an oxidation state of
−1. It can be oxidised to
O2​ (O
0) or reduced to
H2​O (O
−2). So it is also both.
• In
HNO3​, nitrogen has its maximum oxidation state of
+5. It can only be reduced, so it acts solely as an oxidising agent.
• The Reason states that nitrogen does not show multiple stable oxidation states. This is incorrect because nitrogen exhibits a wide range of oxidation states from
−3 (e.g.,
NH3​) to
+5 (e.g.,
HNO3​).
Thus, the Assertion is correct but the Reason is wrong.
Answer:Option A