Discussion
Eo value for various ions are as follows :
Eo(MnO4-) = +1.51 V
E°(Ag/Ag+) = +0.7996 V
Eo(Au/Au+) = +1.692 V
Eo(Zn/Zn2+) = -0.761 V
Based on this data, permaganate can be used to oxidize :
Answer: C
Permanganate can oxidise Zn and Ag.
An oxidant can oxidise a metal when its reduction potential is higher than that of the metal ion/metal couple. Permanganate's couple is +1.51 V. The silver couple is +0.7996 V and the zinc couple -0.761 V, both lower, so MnO4- can oxidise both metals:
\[ \begin{aligned} E^{o}_{cell}(\text{Ag}) &= 1.51 - 0.80 = +0.71\ \text{V} \\ E^{o}_{cell}(\text{Zn}) &= 1.51 + 0.76 = +2.27\ \text{V} \end{aligned} \]
The gold couple, +1.692 V, is above +1.51 V, so for gold the cell potential would be negative and permanganate cannot oxidise it. Every option containing Au is wrong.
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