Question

Equilibrium constant is related to `E^(@)` but not to `E_(cell)`. Explain why?

Answer 1

When equilibrium is reached in the cell reaction, becomes equal to zero. However `E_(cell)^(@)` is a constant quantitiy. Hence, applying Nernst equation to the cell reaction, e.g., to the reaction:
`Zn+Cu^(2+)hArrZn^(2+)+Cu`,
`E_(cell)=E_(cell)^(@)-(RT)/(nF)"ln"([Zn^(2+)])/((Cu^(2+)))=E_(cell)^(@)-(RT)/(nF)"ln "K_(c)`, At equilibrium `E_(cell)=0`. hence, `E_(cell)^(@)=(RT)/(nF)"ln "K_(c)`.