Question

$Cu^+(aq) $ is unstable in solution and undergoes simultaneous oxidation and reduction according to the reaction $2Cu^+(aq) \rightleftharpoons Cu^{2+}(aq)+Cu(s) $ Choose the correct $E^0 $ for above reaction if $E^0_{Cu^{2+}/Cu^+}=0.34 \, V \, and \, E^0_{Cu^{2+}/Cu^+}=0.15 V $

• A. - 0.38 V
• B. #ERROR!
• C. #ERROR!
• D. - 0.19 V

Answer 1

The Correct Option is C

$Δ G^0=-nFE^0 $
From given data,
$(i) Cu(s) \rightarrow Cu^{2+}(aq)+2e^-, $
$\, \, \, \, \, \, \, \, ΔG^0_1=-2(-0.34) \times F $
$(ii) Cu^{2+}(aq)+e^- \rightarrow Cu^+(aq), $
$\, \, \, \, \, \, \, \, \, \, \, Δ G^0_2=-1(0.15) \times F $
On addition,
$\, \, \, \, \, \, \, \, Cu(s) \rightarrow Cu^+(aq)+e^-, $
$ΔG^0_3=-1 \times E^0 \times F $
$ΔG^0_3=ΔG^0_1+ΔG^0_2 $
$-n_3FE^0=-n_1FE^0_1-n_2FE_2 $
$-E^0=-2(-0.34)-1(0.15) $
$\, \, \, \, \, =(-2 \times -0.34)+(-1 \times 0.15) $
$-E^0=+0.68-0.15=0.53 $
or $\, \, \, E^0=-0.53 \, V $
Reaction $2Cu^+ (aq) \rightleftharpoons Cu^{2+}(aq)+Cu(s), $
$\hspace20mm E^0=? $
So, $Cu^+(aq)+e^- \rightleftharpoons Cu(s), \, \, \, \, \, \, \, E^0=0.53 \, V $
$Cu^+(aq) \rightleftharpoons Cu^{2+}(aq)+e^-, $
$\hspace15mm E^0=-0.15 \, V $
$2Cu^+(aq) \rightleftharpoons Cu^{2+}(aq)+Cu(s), $
$\hspace15mm E^0=+0.38 \, V $