1. CELL
(Electrochemical cell)
MRS. RENU DHETARWAL (SERIAL NO. - 27)
ASSISTANT PROFESSOR
DEPARMENT OF CHEMISTRY
GOVT. BANGAUR COLLEGE DIDWANA,NAGAUR(RAJ.)
2. Cell
or
❖ What is cell or battery ?
A battery is a set of
voltaic cells that are
connected in parallel.
3.
4. An electrochemical cell is a device that can generate electrical
energy from the chemical reactions occurring in it, or use the
electrical energy supplied to it to facilitate chemical reactions in it.
These devices are capable of converting chemical energy into
electrical energy, or vice versa.
Electrochemical cell
Types of cell
2 . Galvanic Or Voltaic Cell ( convert chemical energy into
electrical energy)
1 . Electrolytic Cell ( convert electrical energy into chemical energy)
5. Galvanic or Voltic Cell –
In a Galvanic cell ,electrical energy is produced by a
chemical redox reaction. The cell consists of two half-cells
connected via a salt bridge or permeable membrane. The
electrodes are immersed in electrolytic solutions in each
half cell and electrode are connected through an
ammeter.
.The electrode at which oxidation occurs is called the anode
while the electrode at which reduction occurs is called the
cathode .
6. . Consider ,for instance, a copper rod
dipping in a solution of copper sulphate
and a zinc rod dipping in a solution of
zinc sulphate, as in the Daniel cell.
. Both metal rod or electrode are
connected through ammeter and the
two solutions are connected through
salt bridge .
. As soon as the circuit complete
currents start flowing which is indicated
by deflection in the ammeter.
7. • The zinc metal passes into the
solution as Zn2+
ions liberated two electrons
( Zn(s) → Zn2+
(aq) + 2 e− ) .
The process involves oxidation.
8. The liberated electrons move into
the ammeter and then enter the
copper rod. Cu2+Ions extract two
electrons each from the copper rod
and are discharged as copper metal
on the copper electrode
Cu2+
(aq) + 2 e− → Cu(s .
the process involves reduction.
9. ❖ The overall chemical reaction taking place in the galvanic cell ,
usually called the cell reaction . is thus,
Zn + Cu2+ → Zn2+ + Cu
❖ During the reaction, the zinc electrode will be used and the metal
will shrink in size, while the copper electrode will become larger due
to the deposited Cu that is being produced. A salt bridge is necessary
to keep the charge flowing through the cell. Without a salt bridge,
the electrons produced at the anode would build up at the cathode
and the reaction would stop running.
12. Voltaic cells are driven by a spontaneous chemical
reaction that produces an electric current through an
outside circuit. These cells are important because they are
the basis for the batteries that fuel modern society. But
they are not the only kind of electrochemical cell.
The reverse reaction in each case is non-spontaneous and
requires electrical energy to occur.
13. Electrode Sign :
The sign of the anode and cathode in the voltaic or galvanic cells are opposite
to those in the electrolytic cells.
In galvanic cell , Negative charge development on Zn plate and positive
charge development on Cu plate .
15. ❖Any electrode will behavious like anode or cathode
which is based on their electrode potential
16.
17. Measurement of Electrode Potential
The absolute value of the electrode potential of a single electrode
(called single electrode potential) can not be determined because
oxidation half cell reaction or reduction half cell reaction cannot
takes place. It can only be measured by using some electrode as the
reference electrode. The reference electrode used is the standard or
normal hydrogen electrode (SHE or NHE).
