Question

HNO3 is an oxidizing agent but H3PO4 is not . Explain.

Answer 1

The inability of nitrogen atom to unpair and promote its 2s electrons results in the penta positive state of nitrogen, being less stable than tri positive.
Thus, HNO3 where nitrogen is in +5 oxidation state is an oxidizing agent.
On the other hand P has d-orbitals to expand its octet and also shows no inert pair effect, is quite stable in V state.
Thus, H3PO4 in which P is in +5 oxidation state is not oxidizing.

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