For the reduction of \(\mathrm{NO}_{3}^{-}\)ion in an aqueous solution, \(\mathrm{E}^{0}\) is +0.96 V. Values of \(\mathrm{E}^{0}\) for some metal ions are given below \[ \begin{array}{ll} \mathrm{V}^{2+}(\mathrm{aq})+2 \mathrm{e}^{-} \rightarrow \mathrm{V} & \mathrm{E}^{0}=-1.19 \mathrm{~V} \\ \mathrm{Fe}^{3+}(\mathrm{aq})+3 \mathrm{e}^{-} \rightarrow \mathrm{Fe} & \mathrm{E}^{0}=-0.04 \mathrm{~V} \\ \mathrm{Au}^{3+}(\mathrm{aq})+3 \mathrm{e}^{-} \rightarrow \mathrm{Au} & \mathrm{E}^{0}=+1.40 \mathrm{~V} \\ \mathrm{Hg}^{2+}(\mathrm{aq})+2 \mathrm{e}^{-} \rightarrow \mathrm{Hg} & \mathrm{E}^{0}=+0.86 \mathrm{~V} \end{array} \] The pair(s) of metals that is(are) oxidized by \(\mathrm{NO}_{3}^{-}\)in aqueous solution is(are)

(A) V and Hg; (B) Hg and Fe; (D) Fe and V

JEE Advanced · 2009 · 12 Apr 2009 · Paper 2 · Redox Reactions and Electrochemistry

For the reduction of

NO_{3}^{-}

ion in an aqueous solution,

E^{0}

is +0.96 V. Values of

E^{0}

for some metal ions are given below

V^{2 +} (aq) + 2 e^{-} \to V Fe^{3 +} (aq) + 3 e^{-} \to Fe Au^{3 +} (aq) + 3 e^{-} \to Au Hg^{2 +} (aq) + 2 e^{-} \to Hg E^{0} = - 1.19 V E^{0} = - 0.04 V E^{0} = + 1.40 V E^{0} = + 0.86 V

The pair(s) of metals that is(are) oxidized by

NO_{3}^{-}

in aqueous solution is(are)

Answer: (A), (B), (D)

For a metal to be oxidized by

NO_{3}^{-}

, its standard reduction potential must be less than +0.96 V. Comparing the given values: V (−1.19 V), Fe (−0.04 V), and Hg (+0.86 V) all have

E^{0} < 0.96

V, so they can be oxidized. Au (+1.40 V) has

E^{0} > 0.96

V, so it cannot be oxidized by

NO_{3}^{-}

. Therefore, the pairs are V and Hg, Hg and Fe, and Fe and V.

JEE Advanced · 2009 · 12 Apr 2009 · Paper 2 · One or more correct options