There are two principal types of electrochemical cells. A galvanic cell is an electrochemical cell that produces electricity as a result of spontaneous reaction occurring inside it. An electrolytic cell is an electrochemical cell in which a non-spontaneous reaction is driven by an external source of current. any redox reaction may be expressed in terms of two half reactions which are conceptual reactions showing the lowss and gain of electrons. each half reaction has a difinite value of standard electrode potential. the overall reaction is represented by a universally accepted method. knowing the standard electrode potential of the half reactions, the standard EMF of the cell can be calculted. the standard EMF further helps in the calculation of free energy change, equilibrium constant of the cell reaction as well as parameters like solublity products of a sparingly soluble salt. a cell can also be set up in which the two electrodes may be of the same (type, e.g., both may be hydrogen electrodes but the concentration of H^(+) ions in the two solutions may be different. Such cells are called concentration cells. Q. The standard reduction for two reactions are given below: AgCl(s)+e^(-)toAg(s)+Cl^(-)(aq),E^(@)=0.22V Ag^(+)(aq)+e^(-)toAg(s),E^(@)=0.80V The solubility product of AgCl under standard conditions of temperature (298K) is given by