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Sunday, August 14, 2011

CBSE Chemistry: Oxidation - Reduction for class 10

Oxidation in terms of gain of oxygen and reduction in terms of loss of oxygen 

The reaction of a substance with oxygen is called oxidation
2Mg(s) + O2(g) ----------> 2MgO(s)

CH4(g) + 2O2(g)-------->CO2(g) + 2H2O(l)

C6H12O6(s) + 6O2(g) -------> 6CO2(g) + 6H2O(l)

Reduction can be seen as the inverse process where oxygen is removed:

CuO(s) + H2(g) ---------->  Cu(s) + H2O(g) on heating

Fe2O3(s) + 3CO(g) --------->  2Fe(l) + 3CO2(g) in blast furnace

Oxidation in terms of loss of electrons and reduction in terms of gain of electrons

The reaction of magnesium with oxygen

2Mg(s) + O2(g) --------->  2MgO(s)  gives a compound containing Mg2+ ions.

The reaction of magnesium with chlorine gives ionic magnesium chloride

Mg(s) + Cl2(g) ------->  MgCl2(s)

which also contains Mg2+ ions. From the point of view of the magnesium the same process has occurred:


Mg ----> Mg2+ + 2 e-


Therefore oxidation is loss of electrons.

The reaction of copper(II) oxide with hydrogen is reduction according to the first definition; it also results in copper(II) ions changing to copper metal, i.e.

Cu 2+   +   2 e -  --------->  Cu     so that reduction is gain of electrons.

Oxidation and reduction occur during electrolysis:
At the anode electrons are removed from the negative ion  ---->    at theAnode you get oxidation.
At the cathode electrons are added to the positive ion      ------->   at the Cathode you get reduction.

More post describing redox reaction
.These are reactions where electrons are transferred from one species (atom, molecule or ion) to another. We can write 'half' equations to show only what happens to the species losing electrons or a different 'half' equation to show the species gaining electrons..Read more

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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