The electrode potential, `E^(@)`, for the reduction of `MnO_(4)^(-)" to "Mn^(2+)` in acidic medium is `+1.51V`. Which of the following metal(s) will be oxidised? The reduction reactions and standard electrode potentials for `Zn^(2+), Ag^(+) and Au^(+)` are given as
`Zn_((aq))^(2+)+2e^(-)rarrZn_((s)),E^(@)=-0.762V`
`Ag_((aq))^(+)+e^(-)hArr Ag_((x)), E^(@)=+0.80V`
`Au_((aq))^(+)+e^(-)hArr Au_((s)), E^(@)=+1.69V`

Options

A. Zn and Au
B. Ag and Au
C. Au
D. Zn and Ag

Answer

To determine which metals will be oxidized by the reduction of \( \text{MnO}_4^- \) to \( \text{Mn}^{2+} \) in acidic medium, we need to compare the standard electrode potentials of the metals provided with the electrode potential of the reduction reaction of \( \text{MnO}_4^- \).

### Step-by-Step Solution:

1. **Identify the Reduction Reaction and its Electrode Potential**:
The reduction reaction is:
\[ \text{MnO}_4^- + 8\text{H}^+ + 5e^- \rightarrow \text{Mn}^{2+} + 4\text{H}_2\text{O} \]
The standard electrode potential for this reaction is given as \( E^\circ = +1.51 \, \text{V} \).

2. **List the Reduction Potentials of the Metals**:
The reduction potentials for the metals are:
- For \( \text{Zn}^{2+} + 2e^- \rightarrow \text{Zn} \), \( E^\circ = -0.762 \, \text{V} \)
- For \( \text{Ag}^+ + e^- \rightarrow \text{Ag} \), \( E^\circ = +0.80 \, \text{V} \)
- For \( \text{Au}^+ + e^- \rightarrow \text{Au} \), \( E^\circ = +1.69 \, \text{V} \)

3. **Determine the Oxidation Potentials**:
The oxidation potential of a metal is the negative of its reduction potential. Therefore:
- For \( \text{Zn} \): \( E^\circ_{\text{oxidation}} = +0.762 \, \text{V} \)
- For \( \text{Ag} \): \( E^\circ_{\text{oxidation}} = -0.80 \, \text{V} \)
- For \( \text{Au} \): \( E^\circ_{\text{oxidation}} = -1.69 \, \text{V} \)

4. **Compare the Electrode Potentials**:
The \( \text{MnO}_4^- \) will act as an oxidizing agent and will oxidize the metals that have lower reduction potentials than its own. Thus, we compare:
- \( \text{Zn} \) (oxidation potential \( +0.762 \, \text{V} \))
- \( \text{Ag} \) (oxidation potential \( +0.80 \, \text{V} \))
- \( \text{Au} \) (oxidation potential \( +1.69 \, \text{V} \))

5. **Identify the Metals that will be Oxidized**:
- \( \text{MnO}_4^- \) can oxidize \( \text{Zn} \) and \( \text{Ag} \) because their oxidation potentials are lower than \( +1.51 \, \text{V} \).
- \( \text{Au} \) cannot be oxidized by \( \text{MnO}_4^- \) since its reduction potential is higher than that of \( \text{MnO}_4^- \).

### Conclusion:
The metals that will be oxidized by \( \text{MnO}_4^- \) are \( \text{Zn} \) and \( \text{Ag} \).

### Final Answer:
**Option D: Zn and Ag will be oxidized.**

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