Which of the following species is the best oxidizing agent?

• A. Cl_2
• B. I_2
• C. H_2O_2
• D. Fe^{2+}

Answer: (A)

Verified step by step guidance

1. Understand that an oxidizing agent is a species that gains electrons (is reduced) in a redox reaction. The best oxidizing agent is the one that most readily accepts electrons.
2. Look at the given species: \(\mathrm{Cl_2}\), \(\mathrm{I_2}\), \(\mathrm{H_2O_2}\), and \(\mathrm{Fe^{2+}}\). Consider their tendencies to be reduced by comparing their standard reduction potentials.
3. Recall that halogens like \(\mathrm{Cl_2}\) and \(\mathrm{I_2}\) undergo reduction by gaining electrons to form halide ions: \(\mathrm{Cl_2 + 2e^- \rightarrow 2Cl^-}\) and \(\mathrm{I_2 + 2e^- \rightarrow 2I^-}\). The species with the higher standard reduction potential is the stronger oxidizing agent.
4. Hydrogen peroxide (\(\mathrm{H_2O_2}\)) can act as an oxidizing agent by being reduced to water, and \(\mathrm{Fe^{2+}}\) can be oxidized to \(\mathrm{Fe^{3+}}\), but their standard reduction potentials are generally lower than that of \(\mathrm{Cl_2}\).
5. Compare the standard reduction potentials from a reference table: the higher the potential, the better the oxidizing agent. Since \(\mathrm{Cl_2}\) has a higher standard reduction potential than the others, it is the best oxidizing agent among the given species.