Question

$C{u}^{+}(aq)$ is unstable in solution and undergoes simultaneous oxidation and reduction, according to the reaction
$2\mathrm{Cu}{}^{+}(\mathrm{aq})\rightleftharpoons \mathrm{Cu}{}^{2+}(\mathrm{aq})+\mathrm{Cu}(\mathrm{s})$
choose correct $E^{\circ }$ for above reaction if $E_{C{u}^{2+}/Cu}^{\circ }=0.34V$ and $E_{C{u}^{2+}/C{u}^{+}}^{\circ }=0.15V$

• A. $-0.38V$
• B. $+0.49V$
• C. $+0.38V$
• D. $-0.19V$

Answer 1

Answer: (C)

From given data (From $\Delta G^{\circ }=-n{E}^{\circ }F)$

$(i)Cu(s)⟶C{u}^{2+}(aq)+2e^{-}$

$\Delta G_1^{\circ }=-2\times (-0.34)\times F$

$(ii)C{u}^{2+}(aq)+e^{-}⟶C{u}^{+}(aq)$

$\Delta G_2^{\circ }=-1\times (0.15)F$

On addition

$Cu(s)⟶C{u}^{+}(aq)+e^{-}.\Delta G_3^{\circ }=-1\times E^{\circ }\times E$

$\Delta G_3^{\circ }=\Delta G_1^{\circ }+\Delta G_2^{\circ }$

$=(-2\times -0.34\times F)+(-1\times 0.15\times F)$

$=+0.68F-0.15F=0.53F$

or $E^{\circ }=-0.53V$

Reaction,

$2C{u}^{+}(aq)\rightleftharpoons C{u}^{2+}(aq)+Cu(s)E^{\circ }=$?

So, $C{u}^{+}(aq)+e^{-}\rightleftharpoons Cu(s),E^{\circ }=+0.53V$

$C{u}^{+}(aq)\rightleftharpoons C{u}^{2+}(aq)+e^{-};E^{\circ }=-0.15V$

$2C{u}^{+}(aq)\rightleftharpoons C{u}^{2+}(aq)+Cu(s)E^{\circ }=+0.38V$