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Electrochemistry

Question
CBSEENCH12005998

If E° for copper electrode is + 0.34 V how will you calculate its emf value when the solution in contact with it is 0.1 M in copper ions? How does emf for copper electrode change when concentration of Cu2+ ions in the solution is decreased?

Solution
The emf of an electrode when dipped in different concentrated solution is given by Nernst equation.

ECu2+/Cu = E°Cu2+/Cu+0.0592×log Cu2+

Substituting the given values, we get

 ECu2+/Cu = 0.34 V + 0.0592 log 0.1 V                 = + 0.34 V - [0.0295 log 10] V                 = + 0.34 V - 0.0295 V = + 0.3105 V.

When concentration of Cu2+ ion in the solution decreases the emf of the electrode decreases. In this case it has decreased from 0.34 V to 0.3105 V.