From literature values, it is implied that the change in Gibbs energy of a Cu-Zn voltaic cell is largely due to the difference in Gibbs energy of the bulk metals (solid Cu and solid Zn).

Does temperature affect this?

I was thinking I could use the Nernst equation for this but I don’t know if that would be appropriate.

  • 1
    $\begingroup$ Use Nernst equation for what exactly? You can expect temperature to affect the Gibbs energy, yes. You can still use the Nernst equation but have to perform the calculations at the temperature of interest. $\endgroup$ – Buck Thorn Jan 24 '19 at 10:23

Your question is a bit unclear, since the Gibbs free energy of formation of both metals is 0 by definition, since they are pure elements in standard form. The $\Delta G^\circ$ for the cell is a function of the difference in free energies of formation of the ions $\ce{Zn^2+}$ and $\ce{Cu^2+}$.

One approach you can use to determine the temperature dependence of the $\Delta G$ of the reaction is to use reported values for $\Delta H^\circ_f$ and $S^\circ$ to calculate $\Delta H^\circ$ and $\Delta S^\circ$ for the overall reaction. If you are dealing with a small temperature range, you can assume that these values do not change appreciably with temperature and calculate $\Delta G^\circ$ at different temperatures and standard concentrations using $\Delta G^\circ_T = \Delta H^\circ - T\Delta S^\circ$. You can adjust for different concentrations with $\Delta G = \Delta G^\circ_T+RT\ln Q$. (I'm using the subscript T to indicate that the temp is different from typical standard state, but concentrations are not.)

Otherwise, you need data on the potential of the cell at different temperatures.


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