Voltaic cells tabulating

CELL POTENTIALS UNDER STANDARD CONDITIONS We see that an important characteristic of a voltaic cell is its cell potential, which is the difference in the electrical potentials at the two electrodes and is measured in units of volts. Half-cell potentials are tabulated for reduction half-reactions under standard conditions standard reduction potentials). 

The standard cell potential of a voltaic cell, depends on the particular cathode and anode half-cells. We could, in principle, tabulate the standard cell potentials for all possible cathode/anode combinations. However, it is not necessary to undertake this arduous task. Rather, we can assign a standard potential to each half-cell and then use these half-cell potentials to determine Etea- The cell potential is the difference between two half-cell potentials. By convention, the potential associated with each electrode is chosen to be the potential for reduction at that electrode. Thus, standard half-cell potentials are tabulated for reduction reactions, which means they are standard reduction potentials, denoted Ered- The standard cell potential, ceU> is the standard reduction potential of the cathode reaction, (cathode), minus the standard reduction potential of the anode reaction, (anode) ... 

The emf or cell pofenfial of a voltaic cell depends on the particular cathode and anode half-cells involved. We could, in principle, tabulate the standard cell potentials for all possible cafhode/anode combinations. However, it is not necessary to undertake this arduous task. Rather, we can assign a standard potential to each individual half-cell, and fhen use these half-cell potentials to determine Eceii ... 

We have thus far used the tabulation of standard reduction potentials to examine voltaic cells. We can also use E°ed values to understand aqueous reaction chemistry. Recall, for example, the reaction between Zn(s) and Cu aq) shown in Figure 20.3. 

The emf of a voltaic cell depends on the concentrations of substances and the temperature of the cell. For purposes of tabulating electrochemical data, it is usual to choose thermodynamic standard-state conditions for voltaic cells. The standard emf, eii> is the emf of a voltaic cell operating under standard-state conditions (solute concentrations are each 1 M, gas pressures are each 1 atm, and the temperature has a specified value—usually 25°C). Note the superscript degree sign (°), which signifies standard-state conditions. ... 

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