    Electrode is an electrical conductor which         Volt meter : It measures the electric current.
     provides the physical interface between            In Galvanic cells, this shows how much
     the electrical circuit providing the energy        current is produced; in Electrolytic cells, this
     and the electrolyte.                               shows how much current is charging the
                                                        system.
ELECTROCHEMICAL CELL
                                                        Faraday"s Laws of Electrolysis
    In electrochemical cells Redox reactions
     take place.                                        First law of electrolysis states that the weights
    It consist of two electrodes: an anode (the        of substances formed at an electrode during
     electrode at which the oxidation reaction          electrolysis are directly proportional to the
     occurs) and a cathode (the electrode at            quantity of electricity that passes through the
     which the reduction reaction occurs).              electrolyte.
    There are two types of electrochemical              WQ
     cells: Galvanic Cell (ones that                    or W  ZQ  Z. It
     spontaneously produce electrical energy)
     and Electrolytic Cell (ones that consume           Charge = Current x time
     electrical energy).
                                                        Z = electrochemical constant for a given
Galvanic Cell or Daniel cell or Voltaic cell            substance.
It induces a spontaneous redox reaction to              Second law of electrolysis states that the
create a flow of electrical charges, or                 weights of different substances formed by the
electricity.                                            passage of the same quantity of electricity are
                                                        proportional to the equivalent weight of each
It turns chemical energy into electrical energy
                                                        substance.
Non-rechargeable batteries are examples of               W E
Galvanic cells.                                            W      E
                                                        or 1  1
                                                           W2    E2
Oxidation: Zn(S) →Zn2+(aq) + 2e- (Anode)
                                                        Battery
Reduction: 2e- + Cu2+(aq) → Cu(S) (Cathode)
                                                           It is a source of electrical energy, which is
Electrolytic Cell
                                                            provided by one or more electrochemical
    An Electrolytic cell is one kind of battery            cells of the battery after conversion of
     that requires an outside electrical source to          stored chemical energy.
     drive the non-spontaneous redox reaction.             Primary batteries irreversibly transform
    It turns electrical energy into chemical               chemical energy to electrical energy.
     energy                                                 When the supply of reactants is exhausted,
    Rechargeable batteries act as Electrolytic             energy cannot be readily restored to the
     cells when they are being recharged.                   battery.
    Oxidation: Cu(S) → Cu2+(aq)+ 2e- (anode)              Secondary batteries can be recharged;
    Reduction:        Zn2+(aq)+2e- → Zn(S)                 that is, they can have their chemical
     (cathode)                                              reactions reversed by supplying electrical
                                                            energy to the cell, approximately restoring
                                                            their original composition.
                                                   280