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THE REDOX REACTION

     


   The reduction-oxidation reaction pervades all chemistry and biology.  The name is nothing to do with actual reaction process.  Oxidation is the loss of electrons from the molecules and the reduction is the gain of electrons by the molecules.

      An example :  We have seen festival fire works.  The festival crackers contains magnesium.  When the Mg is lit up, it burns brightly.  Here Mg reacts with atmospheric oxygen and produce magnesium oxide (MgO2).  Mg lost two negative electrons(oxidation) and oxygen gained the same 2 electrons (reduction).  Hence, positive ions of magnesium forms bond with negative oxygen ions.  Also energy is released as heat and light.  Here the 'Oxidation" name is justified.  Whenever there is oxidation,  reduction must also accompany it. 


     There are many examples for 'Redox' reaction like, extracting iron from ore; corrosion; combustion in vehicles; photosynthesis; respiration; metabolism; etc. 

     Today, we highly depend on batteries.  We use heavy lead-acid batteries in all the vehicles.  Lap-top, mobiles and tablets work using light lithium -ion batteries.  Redox reaction is the main stay of these batteries.

     In chemical batteries, the oxidation and reduction reaction are spatially separated.  At  negative electrode, electrons are released (oxidation) and at the positive electrode, electrons are absorbed and utilized in reduction reaction.  When the two electrodes are connected, electrons will flow from negative end to positive end and the reactions are completed. So the electric current is established.

     Lead acid battery -working:
    At the negative plate, lead reacts with sulfuric acid and forms lead sulfate and releases two electrons.
     Then the electrons flow to other end.
    At positive plate, lead oxide reacts with sulfuric acid and produces lead sulfate + water. Here the two electrons utilized.

     If you send the current through the battery, reverse reaction takes place.  That is what we call 'charging' and it is also basis for the electrolysis process.
    The redox reactions keep our gadgets and ourselves alive.

Note:  Cut an apple. keep the two halves in open air. the color changes to brownish yellow. The redox reaction takes place due to oxygen in the air.  

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