Question

oxygen is acting as an oxidizing agent in all of the following reactions except
a.
2 c(s) + o₂(g) → 2 co(g)
b.
s(s) + o₂(g) → so₂(g)
c.
2 f₂(g) + o₂(g) → 2 of₂(g)
d.
2 na(s) + o₂(g) → na₂o₂(s)
e.
2 mg(s) + o₂(g) → 2 mgo(s)

Explanation:

An oxidizing agent is a substance that gets reduced (gains electrons, oxidation number decreases). We analyze the oxidation number of O in each reaction:

1. In reactions A, B, D, E: O₂ (oxidation number 0) is converted to compounds where O has an oxidation number of -2 (A, B, E) or -1 (D). O gains electrons, so it acts as an oxidizing agent.
2. In reaction C: O₂ (oxidation number 0) is converted to OF₂, where O has an oxidation number of +2. O loses electrons (is oxidized), so it does NOT act as an oxidizing agent (F₂ is the oxidizing agent here).

Answer:

C. $\ce{2 F_{2}(g) + O_{2}(g) → 2 OF_{2}(g)}$