7.
Electrochemical
Reactions
-
Student experiments with dispososable
materials
-
Electrochemical
reactions are special
Redox
reactions = electron transfer reactions.
........The most
important redox reaction is the combustion of fuels (oil, coal, natural
gas, wood, petrol). It provides the energy to keep our civilisation
going:
........Power stations, automobiles, planes, ships and heating
systems are driven by burning fuels. In humans the oxidation of sugars,
fats and proteins releases.the ........energy.necessary for life.
........In all these reactions a direct electron transfer takes
place from the reducing
agent (fuel) to the oxidizing agent (oxygen).
In electrochemical reactions an indirect electron transfer
from the electron
donor (reducing
agent) to the electron acceptor (oxidizing agent) moves through a
metallic
conductor.
........Galvanic cells
(Voltaic cells)
use a spontaneous
chemical reaction to for
electrontransfer through the metallic conductor. Chemical energy is converted into electric
energy.
........In electrolytic
cells electrical work (supplied by a battery) is used as source of
energy to
drive the
reaction into the opposite direction. Electric energy (of the
battery) is ........converted
into chemical energy:.a metal or hydrogen are formed.
Direct
electron transfer reactions between atoms, molecules or ions are
easier to understand than electrochemical reactions. So
three examples of such experiments are presented first:
01 Direct
electron exchange from magnesium to oxygen
02 Direct
electron exchange from metals to copper(II) ions
(microscope) see experience
chemistry
using a microscope
03 Direct
electron exchange from zinc to copper(II) and oxoniumion ions
(quantitatively) compare:
Chart of El-Marsafy).
Devices for testing and measuring
electrochemicals reactions
04
Electric
conductivity TESTS with a LED
05 Electric
conductivity MEASUREMENT
with direct current
06 Electric
conductivity MEASUREMENT with
alternating current
Galvanic
cells (Electrochemical
cells)
07 Indirect electron transfer from zinc to
copper ions 1
08 Indirect electron transfer from zinc to copper ions 2
09 Indirect
electron
transfer from zinc to copper ions 3:
Changing of the electrodes
Microscaling
this experiment
10 Indirect electron transfer from copper to copper ions: Concentration
cell
11 Indirect
electron transfer between different metals: Electrochemical
series
Electrolytic cells
12 Electrolysis of copper chloride in a Blister
13 Raffination of copper by electrolysis
14. Water drop electrolysis on a white
film canister
15 Water electrolysis in a pipette eudiometer,
piezo igniter
16. Water electrolysis in two ampoules and
tests for the elements
Rechargeable
Mono cells
and batteries
Spontaneous
electron transfer from
Cu to Cl2 in a electrochemicals cell (made in 12)
Me02 Zinc and copper in
Galvanic Cells and in an orange
battery
.Me14
Electrolysis of sulfuric acid with lead electrodes by a photo voltaic
current
Me15 Car battery model I:
Assembling a battery from 6
lead cells
Me16 Car battery model
II: Voltage, current,
discharging, recharging
Me17 Model
Fuel Cell
with alcohol and dichromate/sulfuric acid
More redox reactions (Cola can metals)
Me05 Reactions of two
different metals from a Cola can
with acid and copper salt
Me06 Electricity by redox
reactions of the two Cola
can
metals
Me07 What happens with
aluminium and iron while
electricity is flowing?
Me08 Combine three Cola
cells to have one Cola battery
Me09 Electrolysis of salt
water with a Cola can closure
as Anode
Me10 Electrolysis of salt
water with a Cola can tin (Fe) as Anode
Me11 Reactions of
iron(II) and iron(III) salts from electrolysis
..Me12 Galvanic and
Electrolytical Cells from Cola can metals with bead models
back....... ........................first
published: 25.10.2001..........................last modification: 16.04.2007