Standard reaction entropy from cell potential

The standard reaction entropy from the standard cell potential... 

We see from eqn 5.18 that the standard cell potential increases with temperature if the standard reaction entropy is positive and that the slope of a plot of potential against temperature is proportional to the reaction entropy (Fig. 5.13). An implication is that if the cell reaction produces a lot of gas (corresponding to a positive reaction entropy), then its potential will increase with temperature. The opposite is true for a reaction that consumes gas. 

Equations 20.176 and 20.179 emphasise the essentially thermodynamic nature of the standard equilibrium e.m.f. of a cell or the standard equilibrium potential of a half-reaction E, which may be evaluated directly from e.m.f. meeisurements of a reversible cell or indirectly from AG , which in turn must be evaluated from the enthalpy of the reaction and the entropies of the species involved (see equation 20.147). Thus for the equilibrium Cu -)-2e Cu, the standard electrode potential u2+/cu> hence can be determined by an e.m.f. method by harnessing the reaction... 

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