Final answer:
In the reaction HNO3 + S -> H2SO4 + NO, sulfur is being oxidized (oxidation number increases from 0 to +6), and nitrogen in HNO3 is being reduced (oxidation number decreases from +5 to +2). The oxidizing agent is nitric acid (HNO3) and the reducing agent is elemental sulfur (S).
Step-by-step explanation:
To identify the oxidizing agent and the reducing agent in the provided redox reaction HNO3 + S → H2SO4 + NO, we must assign oxidation numbers to each element and determine which element's oxidation number changes during the reaction.
In this reaction:
- HNO3 contains nitrogen with an oxidation number of +5, and hydrogen with an oxidation number of +1. The oxygen, as usual, has an oxidation number of -2.
- Sulfur (S) in its elemental form has an oxidation number of 0.
- In H2SO4, sulfur has an oxidation number of +6, and the hydrogens each have an oxidation number of +1.
- In NO, nitrogen has an oxidation number of +2.
Comparing the changes, sulfur increases from 0 to +6, indicating it is being oxidized, while nitrogen decreases from +5 to +2, meaning it is being reduced.
Therefore:
- The compound containing the element that increases oxidation number is: S (elemental sulfur).
- The compound containing the element that decreases oxidation number is: HNO3 (nitric acid).
- The reactant serving as the oxidizing agent: HNO3.
- The reactant serving as the reducing agent: S (elemental sulfur).