Strongest Oxidizing Agent

Question

Consider the following half-reactions. Which of these is the strongest oxidizing agent listed here?

I2(s) 2 e- => 2 I-(aq) Eo = 0.53 V

S2O82-(aq) 2 e- => 2 SO42-(aq) Eo = 2.01 V

Cr2O72-(aq) 14 H 6 e-=> Cr3 (aq) 7 H2O(l) Eo = 1.33 V

1. I2(s)

2. I-(aq)

3. S2O82-(aq)

4. SO42-

5. Cr2O72-

6. Cr3 (aq)

Answer 1

First of all, I-, SO4(2-), and Cr3+ are not the oxidizing agents in these half-reactions, they are the reducing agents in the reverse half-reactions. Possible oxidizing agents are I2, S2O8(2-), and Cr2O7(2-). The reagent with the highest reduction potential is the strongest oxidizing agent. That turns out to be S2O8(2-), also known as the peroxydisulfate ion.