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)
n Me02 Zinc and copper in Galvanic Cells and in an orange battery
n .Me14 Electrolysis of sulfuric acid with lead electrodes by a photo voltaic current
n Me15 Car battery model I: Assembling a battery from 6 lead cells
v Me16 Car battery model II: Voltage, current, discharging, recharging
n Me17 Model Fuel Cell with alcohol and dichromate/sulfuric acid

More redox reactions (Cola can metals)
n Me05 Reactions of two different metals from a Cola can with acid and copper salt
v Me06 Electricity by redox reactions of the two Cola can metals
n Me07 What happens with aluminium and iron while electricity is flowing?
n Me08 Combine three Cola cells to have one Cola battery
b Me09 Electrolysis of salt water with a Cola can closure as Anode
v Me10 Electrolysis of salt water with a Cola can tin (Fe) as Anode
b Me11 Reactions of iron(II) and iron(III) salts from electrolysis
b ..Me12 Galvanic and Electrolytical Cells from Cola can metals with bead models 


back....... ........................first published: 25.10.2001..........................last modification: 16.04.2007