Given the standard potentials: ; ; ; ; . Which of the following solid metals can be oxidized by aque — Electrochemistry Chemistry Question
Question
Given the standard potentials: $V^{2+} + 2e^- \rightarrow V, E^\circ = -1.19\text{ V}$; $Fe^{3+} + 3e^- \rightarrow Fe, E^\circ = -0.04\text{ V}$; $Au^{3+} + 3e^- \rightarrow Au, E^\circ = +1.40\text{ V}$; $Hg^{2+} + 2e^- \rightarrow Hg, E^\circ = +0.86\text{ V}$; $NO_3^- + 4H^+ + 3e^- \rightarrow NO + 2H_2O, E^\circ = +0.97\text{ V}$. Which of the following solid metals can be oxidized by aqueous $NO_3^-$ in an acidic medium under standard conditions?
💡 Solution & Explanation
For aqueous $NO_3^-$ to spontaneously oxidize a metal, the standard reduction potential of the nitrate reduction half-reaction ($+0.97\text{ V}$) must be strictly greater than the standard reduction potential of the metal ion/metal couple. Comparing the values: $0.97 > -1.19 (V)$, $0.97 > -0.04 (Fe)$, and $0.97 > +0.86 (Hg)$. However, $0.97 < +1.40 (Au)$. Therefore, $V$, $Fe$, and $Hg$ will be oxidized.