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21 Chemistry -- Oxidation and Reduction

Define the terms on the basis of classical concept: OxidationReductionReducing agentOxidizing agent

Define the terms on the basis of classical concept: 


  • Oxidation

  • Reduction

  • Reducing agent

  • Oxidizing agent

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On the basis of classical concepts, definitions of following terms are:

  • Oxidation: The addition of oxygen or electronegative radical/element; or removal or hydrogen or electropositive element/radical is said to be oxidation.
  • Reduction: The addition of hydrogen or electropositive radical/element or removal or oxygen or electronegative element/radical is said to be reduction.
  • Reducing agent: A substance that experiences increase in Oxidation number of one or more of its elements is said to be a reducing agent.
  • Oxidizing agent: A substance that experiences decrease in Oxidation number of one or more of its elements is said to be an oxidizing agent.

More questions on Oxidation and Reduction

Notes of oxidation and reduction. anyone please.?!?

In terms ofClassical idea:

Oxidation: Addition of oxygen or any other electronegative element to a substance .Conversely , Removal of Hydrogen or any other electropositive element from a substance.

Mg (s) + S (s) MgS (s)

Similarly,Reductionis just opposite process of oxidation.

2FeCl3(aq) + H2(g)2FeCl2(aq) + 2HCl (aq)

In terms ofElectron transfer reaction:
Oxidation: Loss of electron
Reduction: Gain of electron
Oxidant: Acceptor of electron
Reductant: Donor of electron

  • Oxidation number simply denotes...

Differences between O.N. and Valency


O.N. Valency
It is the charge appeared on the atom.
eg: O.N. of C in HCHO is 0.		 It is the no. of electrons lost, gained or shared by an atom of an element.
eg: Valency of C in HCHO is 4.
It may be zero, positive, negative or even in fraction.
eg: O.N. of N in (hydrozoic acid) N3H is -1/3 and in NH3is -3.		 It is a whole number with positive or negative sign.
eg: Valency of N in N3H and NH3is 3.
It may be different for the same element in the different compounds.
eg: O.N. of C in CH4, CH3Cl,...

Define the terms on the basis of electronic concept: OxidationReductionReducing agentOxidizing agent

Define oxidation number. Write the general rules for assigning oxidation number?

Calculate the oxidation number of the underlined elements:

Let the oxidation number of each element to be found be x in each cases.

Here,ON of K, H = 1;ON of O = -2

a) KMnO4

It is a molecule hence, the ON of the molecule is zero.

1 + x + 4(-2) = 0

1 + x - 8 = 0

x - 7 = 0

x = 7

b) K2Cr2O7

It is a molecule hence, the ON of the molecule is zero.

2(1) + 2(x) + 7(-2) = 0

1 + x - 7 = 0

x - 6 = 0

x = 6

c) H2SO4

It is a molecule hence, the ON of the molecule is zero.

2(1) + x + 4(-2) = 0

2 + x - 8 = 0

x - 6 = 0

x = 6

d) CO32-

It is a radical that has -2 charge so, the ON of the...

Define the terms on the basis of oxidation number concept: OxidationReductionReducing agentOxidizing agent

Do as instructed in picture:

Calculate oxidation number of sulphur in caro's acid or peroxy monosulphuric acid. 

Calculate oxidation number of sulphur in marshall's acid or peroxy disulphuric acid.

Calculate the oxidation number of Cr in CrO5.

let it be x. from structure , it's 4 O-atoms are peroxide.

x + (-2x 1 ) + ( -1 x 4 ) = 0

thus, X = + 6

Calculate oxidation number of S atom in Na2S2O3

What is redox reaction. Write the rules for balancing oxidation by oxidation number method.

Do as instructed in picture:

Write the rules for balancing oxidation by ion electron method. 

Do as instructed in picture:

Define electrolysis. Write factors affecting electrolysis.

Explain all the Faraday's  law of electrolysis. Write significance of the law of electrolysis.

What are the differences between valency and oxidation number?


Oxidation State Valency
Total number of electrons and atom can share lose or gain in order to form a bond with another atom. Total number of electrons present in the valence shell of any atom.
Represents the electrical charge of any electron in an atom.

Does not represent the electrical charge of any electron in an atom.
For any pure element, oxidation number is always zero For any pure element, its valency depends upon the total number of electrons present it's valence shell.
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