Concept:An oxidizing agent removes electrons from another substance, meaning the oxidizing agent itself gets reduced (its oxidation state decreases).
Solution:- We must find the reaction where Hydrogen's oxidation state decreases from \( 0 \) to a negative value.
- In option C: \( 2Na + H_2 \rightarrow 2NaH \).
- Sodium is a highly electropositive Group 1 metal (it desperately wants to lose an electron).
- Elemental Hydrogen (\( 0 \)) is forced to accept an electron from Sodium, becoming the hydride ion (\( H^- \)) with an oxidation state of \( -1 \).
- Because Hydrogen gains electrons and is reduced, it acts as the oxidizing agent.
Why other options are incorrect:In reactions with more electronegative non-metals like Chlorine or Nitrogen, Hydrogen acts as the reducing agent, losing electron density and taking on a \( +1 \) oxidation state.
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