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Oxidation - Reduction Reactions

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Oxidation - Reduction Reactions
"Oxidation is a reaction in which oxygen is added or hydrogen is removed from a substance."
Addition of Oxygen

 Oxygen adds on to magnesium to become magnesium oxide.
2Mg + O2 ----> 2MgO

Removal of Hydrogen
Hydrogen is removed from hydroiodic acid to liberate free iodine.
2HI -----> 2H2        +      I2
"Reduction is a reaction in which oxygen is removed from a substance or hydrogen is added to a substance."
Removal of Oxygen
Oxygen is removed from copper oxide to form copper metal.

CuO      +              CO ---------> Cu                     +  CO2
Black                                          Reddish brown

Addition of Hydrogen

Hydrogen adds to chlorine to form hydrogen chloride gas.
H2 + Cl2 -------> 2 HCl

Oxidation and reduction reactions if occur simultaneously we call these reactions as "redox" reactions.
Example of Redox Reaction
Mg + H2SO4   ----------> MgSO4  + H2

The Effects of Oxidation Reactions
(a)Corrosion:-
Many metals are chemically active elements and get easily affected by substances like moisture, air, acids, etc. Example-Iron articles that are shiny when new, but get coated with a reddish brown powder when left for some time. This process is commonly known as rusting of iron. Rusting eventually causes structural weakness and disintegration of the metal.
When a metal is attacked by substances around it, it is said to corrode and this process is called corrosion. Corrosion causes deterioration of essential properties in a material.

What happens to copper vessels or artifacts when exposed to air and water? 

They slowly get tarnished by acquiring a thin green oxide layer in moist air.  The heaviest metal lead also tarnishes in moist weather. The black coating on silver and the green coating on copper are examples of corrosion in which the oxides formed strongly bond to the surface of the metal, preventing the surface from further exposure to oxygen and consequently slowing down corrosion.

Billions of rupees are lost each year because of corrosion and a huge amount of money is spent in prevention of corrosion and tarnishing of metals. Corrosion causes damage to car bodies, buildings, bridges, iron railings, underground water and sewage pipes, ships and all objects made of metals. Much of this loss is due to the corrosion of iron and steel, although many other metals may corrode as well.

Rancidity : If food materials left for a long time unpleasant change in the flavor and odour of a food is called rancidity. The most important cause of rancidity is the deterioration in fats and fatty foods because of oxidation process. When an oxygen atom replace hydrogen atom in the fatty acid molecule it destabilizes the molecule. Factors which accelerate fat oxidation include, salt, light, water, bacteria, moulds trace metals (iron, zinc, etc.).

Usually substances which retard fat oxidation or rancidity are called antioxidants (such as BHT, BHA, vitamin E, and vitamin C, and spices such as sage and rosemary). These are added to foods containing fats and oil to prevent such spoiling. Keeping food in air tight containers or air tight wrapping also helps to slow down oxidation.

More post describing redox reaction

The Effects of Oxidation Reactions : Many metals are chemically active elements and get easily affected by substances like moisture, air, acids, etc. Example-Iron articles that are shiny when new, but get coated with a reddish brown powder when left for some time. This process is commonly known as rusting of iron. Rusting eventually causes structural weakness and disintegration of the metal.
When a metal is attacked by substances around it, it is said to corrode and this process is called corrosion. Corrosion causes deterioration of essential properties in a material..............Read more

In our daily life we come across phenomena like fading of the colours of the clothes, burning of combustible substances like cooking gas, wood and coal, .................................... Read more  
science class 10 oxidation, reduction and redox chemical reaction

Chemistry x - OXIDATION AND REDUCTION : Oxidation: A chemical reaction which involves addition of oxygen or removal of hydrogen or loss of electron(s) is called as oxidation.
2Mg + O2 →2MgO (addition of oxygen)
H2S + Br2 → 2HBr + S (removal of hydrogen)
Fe2+ → Fe3+ + e- (loss of electron)           ..........................................................,,,,,,,,,Read more

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  1. UnknownSeptember 22, 2012

    Excellent blog to understand the redox reaction.I just want to ask that when nitrogen is oxidize then nitrous oxide formed so is it a redox reaction.
    N2 + 2 O2=2N02
    Oxidation States

    ReplyDelete

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