Question:

Given that
\(E^{\ominus}_{\mathrm{O_2/H_2O}} = 1.23\ \mathrm{V}\);
\(E^{\ominus}_{\mathrm{S_2O_8^{2-}/SO_4^{2-}}} = 2.05\ \mathrm{V}\)
\(E^{\ominus}_{\mathrm{Br_2/Br^-}} = 1.09\ \mathrm{V}\)
\(E^{\ominus}_{\mathrm{Au^{3+}/Au}} = 1.4\ \mathrm{V}\)
The strongest oxidizing agent is :

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All the given potentials are standard reduction potentials; the species with the highest reduction potential is the strongest oxidizing agent.
Updated On: Nov 5, 2026
  • \(\mathrm{O_2}\)
  • \(\mathrm{Au^{3+}}\)
  • \(\mathrm{Br_2}\)
  • \(\mathrm{S_2O_8^{2-}}\)
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The Correct Option is D

Solution and Explanation

The given values are standard reduction potentials. The greater the value of \(E^{\ominus}\) (more positive), the greater the tendency of the species on the oxidized side of the couple to get reduced, i.e. the stronger it is as an oxidizing agent.
Compare: \(\mathrm{O_2}\) (1.23 V), \(\mathrm{S_2O_8^{2-}}\) (2.05 V), \(\mathrm{Br_2}\) (1.09 V), \(\mathrm{Au^{3+}}\) (1.4 V).
Order of oxidizing power: \(\mathrm{S_2O_8^{2-}} \gt \mathrm{Au^{3+}} \gt \mathrm{O_2} \gt \mathrm{Br_2}\).
The highest value is 2.05 V, belonging to \(\mathrm{S_2O_8^{2-}}\).
Answer: (4) \(\mathrm{S_2O_8^{2-}}\)
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