Electrochemistry deals with converting between chemical and electrical energy. It has many applications including batteries, plating objects with metals, and nerve impulses. Electrochemical cells convert one type of energy to the other via redox reactions. They require an electrolyte solution, a conductor for electron transfer, and a salt bridge for ion movement. Batteries contain electrochemical cells and store chemical energy for later electrical use. Common battery types include lead-acid batteries in vehicles and various fuel cells.
2. Electrochemistry is a
branch of chemistry
that deals with the
interconversion of
chemical energy and
electrical energy.
Electrochemistry has
many common
applications in
everyday life.
3. Applications:
-Batteries
-used to plate objects with
decorative metals like gold or
chromium
-transmission of nerve
impulses in biological
systems
Redox chemistry, the
transfer of electrons, is
behind all electrochemical
processes.
4. An
electrochemical
cell is any device
that converts
chemical energy
into electrical
energy or
electrical energy
into chemical
energy.
5. There are three
components that make up an
electrochemical reaction:
1. There must be a
solution where
redox reactions can
occur. These
reactions generally
take place in water
to facilitate electron
and ion movement
6. 2. A conductor must exist for
electrons to be transferred. This
conductor is usually some kind of
wire so that electrons can move
from one site to another.
3. Ions also must be able to
move through some form of
salt bridge that facilitates ion
migration.
7. One of the best
examples of an
electrochemical cell is
a battery. Batteries
consist of one or more
electrochemical cells
that store chemical
energy for later
conversion to
electrical energy.
8. Batteries are composed of at
least one electrochemical cell
which is used for
the storage and generation of
electricity. Though a variety of
electrochemical
cells exist, batteries generally
consist of at least one voltaic
cell.
9. Voltaic cells
are also sometimes
referred to as galvanic
cells. Chemical reactions
and the generation of
electrical energy is
spontaneous within a
voltaic cell, as opposed
to the reactions in
electrolytic cells and
fuel cells.
10. A. Dry cell or
Leclanche cell is a
primary cell, handy
for sporadic use, with
positive anode of zinc
encompassed by a
mixture of manganese
dioxide and powdered
carbon in a pot, which
is porous.
11. The pot and the
negative zinc
terminal remained in
a container holding
ammonium chloride
solution. The
electromotive force
(emf) is nearly 1 -4
volt.
12. Types of Leclanche’s
cell include:
a) zinc (Carbon cathode)
b) zinc chloride
(Ammonium chloride
electrolyte reinstated by
zinc chloride)
c) alkaline manganese
(Ammonium chloride
terminal displaced by
potassium
hydroxide)
13. How it works:
The process which generates
power in a Leclanché cell
starts when zinc
particles on the surface of
the anode oxidize, i.e. when
zinc atoms surrender
their valence electrons to
end up becoming the
positively charged
particles.
14. The zinc particles
move far from the
anode while leaving
their electrons on its
surface that makes
the anode more
negatively charged
than the cathode.
15. At the point when the
cell is associated in an
outer electrical circuit,
the excess electrons
on the zinc anode
gush through the
circuit to the cathode
made up of carbon.
This flow of electrons
frames the electric
current.
17. A standard dry cell
comprises a zinc anode,
usually in the form of a
cylindrical pot, with a
carbon cathode in the form
of a central rod. The
electrolyte
is ammonium chloride in the
form of a paste next to the
zinc anode.
18. B. Button cells are single
cells, usually disposable
primary cells. Common
anode materials are zinc or
lithium. Common cathode
materials are manganese
dioxide, silver oxide,
carbon monofluoride,
cupric oxide or oxygen
from the air.
19. C. Fuel cell can be
defined as an
electrochemical cell
that generates
electrical energy from
fuel via an
electrochemical
reaction.
20. A fuel cell resembles a battery
in many respects, but it can
supply electrical energy over a
much longer period of time.
This is because a fuel cell is
continuously supplied with fuel
and air (or oxygen) from an
external source, whereas a
battery contains only a limited
amount of fuel material and
oxidant that are depleted with
use.
21. For this reason
fuel cells have
been used for
decades in space
probes,
satellites, and
manned
spacecraft.
22. Types of Fuel Cells
Various types of fuel cells
have been developed. They
are generally classified
on the basis of the
electrolyte used, because
the electrolyte determines
the operating temperature of
a system and in part the kind
of fuel that can be
employed.
23. C1. The Polymer Electrolyte
Membrane (PEM) Fuel Cell
The electrolyte used in PEMFCs
is a polymer which has the
ability to conduct protons.
A typical PEM fuel cell consists
of bipolar plates, a catalyst,
electrodes, and the polymer
membrane.
24. C.2. Solid Acid Fuel Cell
A solid acid material is used
as the electrolyte in these
fuel cells. The molecular
structures of these solid
acids are ordered at low
temperatures. At higher
temperatures, a phase
transition can occur which
leads to a huge increase in
conductivity.
25. C.3. Alkaline Fuel Cell
This was the fuel cell which
was used as the primary
source of electricity in the
Apollo space program.
In these cells, an aqueous
alkaline solution is used to
saturate a porous matrix,
which is in turn used to
separate the electrodes.
26. C.3. Alkaline Fuel Cell
(cont.)
The operating
temperatures of these
cells are quite low
(approximately
90oC).
These cells are highly
efficient. They also
produce heat and water
along with electricity.
27. C.4. Solid Oxide Fuel Cell
These cells involve the use of a
solid oxide or a ceramic electrolyte
(such as yttria-stabilized zirconia).
The operating temperatures of
these cells are very high (lower
limit of 600oC, standard operating
temperatures lie between 800 and
1000oC).
28. C.5. Molten Carbonate
Fuel Cell
The electrolyte used in
these cells is lithium
potassium carbonate salt.
This salt becomes liquid at
high temperatures, enabling
the movement of carbonate
ions. Similar to SOFCs,
these fuel cells also have a
relatively high operating
temperature of 650o
29. D. Lead Batteries
A lead storage battery, also known
as a lead-acid battery, is the oldest
type of rechargeable battery and
one of the most common energy
storage devices. Most people are
accustomed to using them in
vehicles, where they have the
ability to provide high currents for
cranking power.
30. D. Lead Batteries (cont.)
Lead-acid batteries have moderate
power density and good response
time. Depending on the power
conversion technology incorporated,
batteries can go from accepting energy
to supplying energy instantaneously.
Lead-acid batteries are affected by
temperature and must be maintained in
order to achieve maximum life
expectancy.
31. D. Lead Batteries (cont.)
Discharging the stored energy
relies on both the positive and
negative plates becoming lead
(II) sulfate and the electrolyte
losing much of its
dissolved sulfuric acid.
Editor's Notes
Use redox reaction
Spontaneous reactions release energy while non-spontaneous use it
An electrolytic cell is an electrochemical cell that uses electrical energy to drive a non-spontaneous redox reaction
electromotive force = work done/ charge
Examples of solid acids include CsHSO4 and CsH2PO4 (cesium hydrogen sulfate and cesium dihydrogen phosphate respectively)
Yttrium oxide and zirconium dioxide (Zr02), Solid oxide fuel cells are limited to stationary applications due to their high operating temperatures.
The anode and the cathode of this cell are vulnerable to corrosion due to the high operating temperature and the presence of the carbonate electrolyte. • These cells can be powered by carbon-based fuels such as natural gas and biogas.
