Iron(II) ions, Fe2+\text{Fe}^{2+}Fe2+, can act as a homogeneous catalyst in the reaction between peroxodisulfate ions, S2O82−\text{S}_2\text{O}_8^{2-}S2O82−, and iodide ions, I−\text{I}^-I−.
Which of the following equations represents the step in this catalytic mechanism in which the iron catalyst is oxidized?
2I−+2Fe3+→I2+2Fe2+2\text{I}^- + 2\text{Fe}^{3+} \rightarrow \text{I}_2 + 2\text{Fe}^{2+}2I−+2Fe3+→I2+2Fe2+
S2O82−+2Fe2+→2SO42−+2Fe3+\text{S}_2\text{O}_8^{2-} + 2\text{Fe}^{2+} \rightarrow 2\text{SO}_4^{2-} + 2\text{Fe}^{3+}S2O82−+2Fe2+→2SO42−+2Fe3+
S2O82−+2Fe3+→2SO42−+2Fe4+\text{S}_2\text{O}_8^{2-} + 2\text{Fe}^{3+} \rightarrow 2\text{SO}_4^{2-} + 2\text{Fe}^{4+}S2O82−+2Fe3+→2SO42−+2Fe4+
S2O82−+2I−→2SO42−+I2\text{S}_2\text{O}_8^{2-} + 2\text{I}^- \rightarrow 2\text{SO}_4^{2-} + \text{I}_2S2O82−+2I−→2SO42−+I2