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:

Step1: Define oxidizing agent

An oxidizing agent gains electrons (oxidation state decreases).

Step2: Check O oxidation state in A

Reaction: $2C(s)+O_2(g)→2CO(g)$. O in $O_2$: 0; in CO: -2. Decrease → oxidizing agent.

Step3: Check O oxidation state in B

Reaction: $S(s)+O_2(g)→SO_2(g)$. O in $O_2$:0; in $SO_2$:-2. Decrease → oxidizing agent.

Step4: Check O oxidation state in C

Reaction: $2F_2(g)+O_2(g)→2OF_2(g)$. O in $O_2$:0; in $OF_2$:+2. Increase → not oxidizing agent.

Step5: Check O oxidation state in D

Reaction: $2Na(s)+O_2(g)→Na_2O_2(s)$. O in $O_2$:0; in $O_2^{2-}$:-1. Decrease → oxidizing agent.

Step6: Check O oxidation state in E

Reaction: $2Mg(s)+O_2(g)→2MgO(s)$. O in $O_2$:0; in MgO:-2. Decrease → oxidizing agent.

Answer:

C. $2 F_2(g) + O_2(g) → 2 OF_2(g)$