The standard reduction potentials at \(298 \mathrm{~K}\) for the following half cells are given below :
\(\begin{array}{ll}
\mathrm{Cr}_2 \mathrm{O}_7^{2-}+14 \mathrm{H}^{+}+6 \mathrm{e}^{-} \rightarrow 2 \mathrm{Cr}^{3+}+7 \mathrm{H}_2 \mathrm{O}, \mathrm{E}^{\circ}=1.33 \mathrm{~V} \\
\mathrm{Fe}^{3+}(\mathrm{aq})+3 \mathrm{e}^{-} \rightarrow \mathrm{Fe} \qquad \mathrm{E}^{\circ}=-0.04 \mathrm{~V} \\
\mathrm{Ni}^{2+}(\mathrm{aq})+2 \mathrm{e}^{-} \rightarrow \mathrm{Ni} \qquad \mathrm{E}^{\circ}=-0.25 \mathrm{~V} \\
\mathrm{Ag}^{+}(\mathrm{aq})+\mathrm{e}^{-} \rightarrow \mathrm{Ag} \quad\qquad \mathrm{E}^{\circ}=0.80 \mathrm{~V} \\
\mathrm{Au}^{3+}(\mathrm{aq})+3 \mathrm{e}^{-} \rightarrow \mathrm{Au} \qquad \mathrm{E}^{\circ}=1.40 \mathrm{~V}
\end{array}\)
Consider the given electrochemical reactions,
The number of metal(s) which will be oxidized be \(\mathrm{Cr}_2 \mathrm{O}_7^{2-}\), in aqueous solution is ______