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