Which among the following is an example of Metal - metal ion electrode?

1. $\mathrm{Fe}^{3+}$ (aq.), $\mathrm{Fe}^{2+}$ (aq.) $\mid \mathrm{Pt}$
2. $\mathrm{Cl}^{-}{ }_{(\text {aq. })}\left|\mathrm{AgCl}_{(\mathrm{s})}\right| \mathrm{Ag}$
3. $\mathrm{Zn}^{2+}$ (aq.) $\mid \mathrm{Zn}_{(s)}$
4. $\mathrm{OH}^{-}$ (aq.) $\left|\mathrm{O}_{ \left.2(\mathrm{~g}), \mathrm{PO}_{2}\right)}\right| \mathrm{Pt}$

Solution

Asked in: MHT CET 2020 (15 Oct Shift 1)

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