The standard reduction potentials at 298 K for the following half cells are given below: Cr_2 O_7^2-+14 H^++6 e^- → 2 Cr^3++7 H_2 O, E^°=1.33 V;…

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