Class 11 Chemistry Redox Reactions Oxidation and Reduction

Oxidation and Reduction

  • In terms of Classical concept

Oxidation: Oxidation is defined as “addition of oxygen or any electronegative element and removal of hydrogen or any electropositive element”.


Reduction: Reduction is defined as” addition of hydrogen or any electropositive element and removal of oxygen or any electronegative element”.


Please note the substance that undergo oxidation itself and reduce other is called reducing agent whereas the substance that undergo reduction itself and oxidize other is called oxidizing agent.

For example:-      CuO       + H2 -->      Cu + H2O

                   Copper Oxide  Hydrogen  Copper Water

In reaction, Cu is undergoing reduction and oxidizing hydrogen. Therefore, Cu is oxidizing agent and H is reducing agent.

“As in this reaction both oxidation and reduction occur simultaneously, therefore reaction is called redox reaction.”

  • In terms of Electron transfer concept

Oxidation: Is defined as loss of electrons that is:

                  M-electron  -->   M+

            Metal             Metal ion

Reduction: Is defined as gain of electrons that is given below.

N + electron  -->  N-

       Non metal           non metal ion

Let us explain it more with the help of example:

Let’s consider equation: H2 + O2 -- > H2O

We can see in this example that H atom as going from neutral to a positive state in water, the O atom goes from zero state to dinegative state in water. There is an electron transfer from H to O and consequently H2  is oxidized and O2 is reduced .The charge transfer is only partial or we can say that it is electron shift rather than calling it as complete loss of electron by H and gain by O.

Another example of Redox reaction in terms of electron transfer:

          Mg +         H2 -->       MgH2

     Magnesium Hydrogen  MagnesiumHydride

In this Magnesium is losing electrons, that is undergoing oxidation and hydrogen is gaining electrons therefore, it is undergoing reduction. Mg is Reducing agent in it and H is Oxidizing agent in it.

  • In terms of oxidation number

Oxidation number: It is defined as “residual charge that is present on atom when the atom is in combined state with other atoms”.

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