1 (10)

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Chapter 2 POTENTIALS AND THERMODYNAMICS OF CELLS Chapter 2 (2) Rearrangement provides Problem 2.8 The cell reaction is (10) Half-Reactions: No terms describing energies in M appear, thus E does not depend on M. The term appeared in equations (1) and (2) above, but they cancelled out. District values of the interfacial potential Net Reactions: difference, would arise for various species M, but the variations would be exactly compensated by variations in Because M is not involved in the overall reaction, it cannot affect the cell potential, which re- flects for this reaction. One can consider the cell at open circuit in terms of the species at equilibrium across various phase boundaries. Problem 2.10 Consistent with the comments at the start of Problem 2.2, a sound thermodynamic development of standard potentials for half-cell reactions must proceed through free energy calculations, not standard potentials. (1) (a). First, convert the two standard half-cell potentials into a net reaction by combining the reac- tions with the half-cell reaction. (2) = Thus, (3) 0.340 V (4) 0.340 (5) and Adding equations (2) to (4) gives 1L (6) Substituting from (1) and (5) and recognizing that Then, note that subtracting the second reaction from the first yields (7) gives This has a standard free energy of (8) (1) Expansion gives This is a single electron transfer reaction, so the emf for this reaction is = (9) (2) 10 11