Equivalent weight of Ag = \(\frac{108}1 = 108 g/equivalent\)
Number of faradays = \(\frac{6.97}{108} = 0.0645 F\)
Let say, oxidation state of Au = +n
∴ Equivalent weight of Au = \(\frac {197}{n} g/equivalent\)
∴ Number of faraday required to deposite 4.25g of Au = \(\frac{4.25\times n}{197}\)
\(\therefore \frac{4.25\times n}{197} = 0.0645\)
⇒ \(n = \frac{0.0345\times 197}{4.25}\)
\(n = 2.989\)
\(n \approx +3\)
Hence oxidation state of Au is +3.