Voltaic cells work done

The cell emf, E, is a positive number for a voltaic cell, so u ax will be a negative number for a voltaic cell. Work done by a system on its surroundings is indicated by a negative sign for iv. (Section 5.2) Thus, the negative value for Wn,ax means that a voltaic cell does work on its surroundings. 

The electromotive force of a voltaic cell is the total amount of work done when unit quantity of electricity passes through the cell. 

In general, the work that can be obtained in an isothermal change is a maximum when the process is performed in a reversible manner. This is true, for example, in the production of electrical work by means of a voltaic cell. Cells of this type can be made to operate isothermally and reversibly by withdrawing current extremely slowly ( 331) the e.m.f. of a given cell then has virtually its maximum value. On the other hand, if large currents are taken from the cell, so that it functions in an irreversible manner, the E.M.F. is less. Since the electrical work done by the cell is equal to the product of the e.m.f. and the quantity of electricity passing, it is clear that the same extent of chemical reaction in the cell will yield more work in the reversible than in the irreversible operation. 

If the E.M.F. of a voltaic cell is E int. volts, and the process taking place within it is accompanied by the passage of N faradays of electricity, i.e., NF coulombs, where F represents 96,600 int. coulombs, the work done by the cell is NFE int. volt-coulombs, or int. joules (cf. 3b). If the cell is a reversible one, as described above, and E is its reversible, i.e., maximum, E.M.F., at a given temperature and pressure, usually atmospheric, it follows from the arguments presented earlier that... 

Cu ions, which enter the solution and make it more concentrated. The electrons released at the anode flow to the cathode compartment. There, Cu"" ions in the concentrated solution pick up the electrons and become Cu atoms, which plate out on the electrode, so that solution becomes less concentrated. As in any voltaic cell, ceii decreases until equilibrium is attained, which happens when [Cu " "] is the same in both half-cells (Figure 21.12B). The same final concentration would result if we mixed the two solutions, but no electrical work would be done. 

As in any voltaic cell, cell decreases nntil equilibrium is attained, which happens when [Cu +] is the same in both half-cells (Figure 21.12B). The same final concentration would result if we mixed the two solutions, bnt no electrical work would be done. 

The electromotive force (emf), or cell potential, is the maximum voltage of a voltaic cell. It can be directly related to the maximum work that can be done by the cell. A standard electrode potential, or reduction potential, refers to the potential of an electrode in which molar concentrations and gas pressures (in atmospheres) have unit values. A table of standard electrode potentials is useful for establishing the direction of spontaneity of an oxidation-reduction reaction and for calculating the standard emf of a cell. 

Any two different half-cells can be combined together to form a voltaic cell and allow the electrons to flow from the reducing agent to the oxidizing agent. The resulting movement of electrons allows useful work to be done and also allows chemists to measure the tendency for a redox reaction to occur. 

When a reaction occurs in a voltaic cell, the cell does work—electrical work. Think of this as the work of moving electric charges. The total work done is the product of three terms (a) (b) the number of moles of electrons... 

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