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Question
Calculate the standard emf of the cell: \[\ce{Cd|Cd^{2+}||Cu^{2+}|Cu}\] and determine the cell reaction. The standard reduction potentials of Cu2+|Cu and Cd2+|Cd are 0.34 V and −0.40 volts respectively. Predict the feasibility of the cell reaction.
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Solution
Cell reactions:
Oxidation at anode:
\[\ce{Cd_{(s)} -> Cd^{2+}_{( aq)} + 2e^-}\] \[\ce{(E^0_{ox})_{{Cd|Cd^{2+}}}}\] = 0.4 V
Reduction at cathode:
\[\ce{Cu^{2+}_{( aq)} + 2e^- -> Cu_{(s)}}\] \[\ce{(E^0_{red})_{{Cu^{2+}|Cu}}}\] = 0.34 V
\[\ce{Cd_{(s)} + 2e^- -> Cd^{2+}_{( aq)} + Cu_{(s)}}\]
`"E"_"cell"^0 = ("E"_"ox"^0)_"anode" + ("E"_"red"^0)_"cathode"`
= 0.4 + 0.34
= 0.74 V
emf is +ve, so ΔG is (−)ve, the reaction is feasible.
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