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Question
EΘ of Cu is + 0.34V while that of Zn is – 0.76V. Explain.
Solution
High ionisation enthalpy to change \[\ce{Cu(s)}\] to \[\ce{Cu^2+}\] is not balanced by hydration enthalpy. Therefore, it exhibits a positive EΘ value. However, \[\ce{Zn}\] exhibits a lower value of ionization enthalpy because a stable 3d10 configuration is attained after losing two electrons. The hydration energy for \[\ce{Zn^2+}\] is comparable to that of \[\ce{Cu^2+}\]. Therefore, E° for Zn is negative.
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