Nernst Equation (2)

Q. What is the cell potential and

the [Zn2+] , [Cu2+] when the cell is completely discharged?

A. When cell is fully discharged:

• chemical reaction is at equilibrium
• E = 0 ?G = 0
• Q = K and thus

0 = Eo - (RT/nF) ln (K)

or Eo = (RT/nF) ln (K)

or ln (K) = nFEo/RT = (n/0.0257) Eo at T = 298 K

So . . . K = e

= 1.5 x 1037

(2)(1.10)/(.0257)

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