At what conditions does equilibrium attain in the galvanic cell. What exactly happens at the equilibrium state of a galvanic cell redox reaction. Consider the setup Zn|Zn2+||Cu2+|Cu, Where

  • Anode: $\ce{Zn -> Zn^2+ + 2e}$
  • Cathode: $\ce{Cu^2+ + 2e -> Cu}$
  • Final reaction: $\ce{Zn + Cu^2+ -> Zn^2+ + Cu}$

Here the electrons would flow from Anode to cathode through a metallic wire which connects the two half cells. There comes a stage where the $\ce{Zn^2+}$ ions get piled up in anode compartment and depletion of $\ce{Cu^2+}$ ions in the cathode compartment. At one stage the reaction stops which is when the cell/battery power is all utilised. But where does the equilibrium state come from? Will the equilibrium reaction occur when the salt bridge is connected? The reason I stressed more on equilibrium state is because of the equilibrium constant appearing in the Nernst equation. I'm pretty much in a confused state reagarding the concept. Any help would be greatly appreciated.

  • $\begingroup$ The nernst equation calculates at what voltage would the hypothetical cell be at equilibrium. At equilibrium, the current is zero. This voltage is then used to create a "ranking" of the (half) reactions so as to predict which will happen "first" or prioritized. $\endgroup$ – Stian Yttervik Mar 8 '17 at 12:40
  • $\begingroup$ when the current becomes zero, how can the cell be at equilibrium, i mean no transfer of electrons takes place due to development of excess potential near respective electrodes. $\endgroup$ – Alchemist Mar 25 '17 at 5:11
  • $\begingroup$ Sure there is transfer of electrons. Just the same amount each direction. Equilibrium. The forward reaction rate equals the backward one. $\endgroup$ – Stian Yttervik Mar 25 '17 at 23:53

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