electrochemistry

1. Electrochemistry
Chapter 12
M. Muhammad Mohsin Rasool
Benchmark College, Islamabad, Pk

2. Electrolytic Conduction VS Electrolytic Conduction
Metallic Conduction Electrolytic Conduction
Conduction in Metals Conduction in Electrolyte
Due to Free Electrons Due to Free Ions
Chemical Properties remains intact Chemical properties alter with the decomposition ions
e.g Sodium, Iron, Nickle e.g Sodium Chloride

3. Cont.
• In Electrolytic conduction, Current IS CARRIED OUT BY POSITIVE OR
NEGATIVE IONS. (EITHER IN AQUEOUS OR MOLTEN State
• Ionization is a process when ionic compounds when fused or
dissolved in water splits into its ions.

4. Electrochemical Cells
The devices that are used to drive spontaneous or
non-Spontaneous reaction.
Types :
1. Electrolytic Cells
2. Galvanic Cells

5. 1. Electrolytic Cell:
• Electrolytic Cell: A cell where a battery forces a redox reaction to occur (non-
spontaneous reaction). Opposite of a voltaic cell.
• Uses:
• 1) To obtain group 1 and group 2 metals. Electrolysis of salts, "Salt splitting".
• 2) Electroplating: plating a metal on top of another (Ex. Gold plated jewelry)

6. Parts of electrolytic cells
• Electrolytic cells have only one cell.
• Electrolytic cells are powered by a battery or power source. Converts electrical
to chemical energy.
• Anode - still the site of oxidation. Assigned as the POSITIVE electrode.
• Cathode - still the site of reduction. Assigned as the NEGATIVE electrode.

7. Electrolytic Cell Diagram:

8. Electrolysis of a Molten Salt:
• Molten salt breaks up into ions in solution
•NaCl(l) → ________________
• Na+ is attracted to negative cathode and is reduced
_______________________
• Cl1- is attracted to the positive anode and is oxidized
________________________

9. Electrolysis of Aqueous Salt:
• Aqueous solutions will always have water (H2O). When aqueous solutions are
electrolysed the products are not always the same as when molten salts are
electrolysed.
• When you electrolyse sodium chloride solution the products at the electrodes
are:
 Anode: chlorine
 Cathode: hydrogen
• The hydrogen at the cathode comes from water. Water is a weak electrolyte.
Water dissociates/ ionise slightly to give hydrogen ions and hydroxide ions.
H2O (l) ⇌ H+ (aq) + OH– (aq)

10. Electrolysis of Aqueous Salt: Cont.

11. Electrolysis
• The electrochemical reactions that occurs are the electrodes during electrolytic
conduction constitute the phenomena of electrolysis.

12. When electrode take part:

13. Galvanic or Voltoic Cell:
• Galvanic cells (aka voltaic cells) are electrochemical cells in which
spontaneous redox reactions produce a flow of electrons, ie
electricity.
Anode : -ive
Cathode: +ive

14. Components of Galvanic Cell:
• Two half cell
• Voltmeter and Wire
• Salt Bridge
• Functions:
• It Neutralizes both compartment
• Provide Connection

15. Working: Voltaic Cells
• A typical cell looks
like this.
• The oxidation occurs
at the anode.
• The reduction
occurs at the
cathode.

16. Working: Voltaic Cells
Once even one
electron flows from
the anode to the
cathode, the
charges in each
beaker would not be
balanced and the
flow of electrons
would stop.

17. • Therefore, we use a
salt bridge, usually a
U-shaped tube that
contains a salt
solution, to keep the
charges balanced.
➢Cations move toward
the cathode.
➢Anions move toward
the anode.
Working: Voltaic Cells

18. • In the cell, then,
electrons leave the
anode and flow
through the wire to
the cathode.
• As the electrons
leave the anode, the
cations formed
dissolve into the
solution in the
anode compartment.
Working: Voltaic Cells

19. • As the electrons
reach the cathode,
cations in the
cathode are
attracted to the now
negative cathode.
• The electrons are
taken by the cation,
and the neutral
metal is deposited
on the cathode.
Working: Voltaic Cells

20. Electrode Potential:
• The potential setup when an electrode is in contact with one molar
solution of its own ions at 298K is known as standard potential or
standard reduction potential of the elements. It is represented as Eo

21. Electromotive Force (emf)
• The potential difference between the
anode and cathode in a cell is called
the electromotive force (emf).
• It is also called the cell potential, and is
designated Ecell.