DIGITAL DIARY
Topic
– REDOX
REACTION
BY –Mrs Nisha Singh, K .V. Chhatarpur ( M.P.)
2. CONTENTS:
1. CLASSICAL IDEA OF REDOX REACTION-OXIDATON AND REDUTION
REATIONS
2. REDOX REACTION IN TERMS OF ELECTRON TANSFR REATIONS
3. OXIDATION NUMBER
4. BALANCING OF REDOX REACTION
5. REDOX REACTION AND ELECTRODE PROCESS
1. Classical idea of Redox Reaction-Oxidation and Reduction Reactions
Oxidation : it is the process of addition oxygen or any more electronegative
element or group or removal of hydrogen or any electropositive element or
group.
example: Mg + O2 = 2MgO
Reduction : It is the process of addition of hydrogen or any electropositive
element or group or removal of oxygen or any other electronegative element
or group.
example : Cl2 + H2 =2HCl
OXIDISING AND REDUCING AGENT



Reduction agent: It is a substance which brings about reduction. Oxidising agent: It
is a substance which brings about oxidation. C + O2 = CO2
Here oxygen will work as oxidising a
N2 +3H2 = 2 NH3
Here hydrogen will work as reducing agent.
2.Redox Reaction in Term of Electron Transfer Reactions
• Oxidation : the process in which an atom or ion loses one or more
electrons.
• example : Na Na+ + e- ( increase in positive valency)
•
S2-  S + 2 e- (decrease in negative valency)
• Reduction : the process in which an atom or ion gains one or more
electrons.
• example : Cl + e-  Cl- (increase in negative valency)
•
Fe + e-  Fe (decrease in positive valency)
* electron losing species is called reducing agent.
* electron accepting species is called oxidising agent.
3.Oxidation Number or Oxidation state  It is the residual charge which an atom actually have or appear to have when
all other atoms or group of atoms are removed as ion from the molecule.
CALCULATION OF OXIDATON STATE
1] IN KMnO4 OF Mn
LET THE O.S. OF Mn BE (X)
K+X+O=0
1 + X + 4(-2) =0
1+X–8=0
[X=7]
OXIDATION NO. CNCEPT OF OXIDATION AND REDUCTION
OXIDATION : IT IS THE PROCESS IN WHICH O.N. OF AN ATOM OF AN ELEMENT
INCREASES.
EXAMPLE : 2Zn + O2 2ZnO
HERE O.S. OF Zn INCREASE.
REDUCTION : IT IS THE PROESS IN WHICH O.N. OF ATOM OF ELEMENT DECREASES.
EXAMPLE : 2Zn + O2 2ZnO
HERE O.N.OF OXYGEN DECREASES.
REDOX REATION : THOSE REACTION IN WHICH OXIDATION AND REDUCTION TAKES
PLACE SIMULTANEOUSLY, ARE CALLED AS REDOX REACTION.
EXAMPLE : CH4 + 4Cl2 CCl4 +4HCl
HERE CARBON GOES OXIDATION WHILE CHLORINE GOES REDUCTION.

OXIDISING AGENT : IT IS DEFINED AS THE SPECIES WHOSE OXIDATION NO.
DECREASES.
 REDUCING AGENT : IT ISDEFINED AS THE SPECIES WHOSE OXIDATION NO.
INCREASES.
TYPES OF REDOX REACTION
1.COMBINATION REACTIONS:
A REDOX REACTION IN WHICH TWO OR MORE ELEMENT
COMBINE TO FORM A PRODUCT.
EXAMPLE: C(g) + O2(g)  CO2(g)
2. DECOMPOSITION REACTIONS:
IN A DECOMPOSITION REACTION A PRODUT DECOMPOSES
IN TWO OR MORE REACTANTS .
EXAMPLE : CaCO3 (s)  CaO(s) + CO2(g)
3. DISPLACEMENT REACTION
IN A DISPLACEMENT REATION, AN ION(OR AN ATOM)IN A COMPOUND IS DISPLACED
BY AN ION (OR AN ATOM) OF ANOTHER ELEMENT.
IT MAY BE DENOTED BY X + YZ XZ + Y
IT IS OF FOLLOWING TYPES
[1] METAL DISPLACEMENT:
CuSO4 + Zn  Cu + ZnSO4
[2] NON-METAL DISPLACEMENT :
Fe + 2HCl FeCl2 + H2
4. DISPROPORNATION REACTION –IT REFERS TO A REACTION IN WHICH SAME
SPECIES UNDRGOES OXIDATION AS WELL AS REDUCTION.
For example : Cl2 + 6NaOH  5NaCl + NaClO3 + 3H2O
HERE CLORINE UNDERGOES OXIDATION AS WELL AS REDUCTION.
BALANCING OF REDOX REACTION
1. ION ELETRON METHOD:
2. OXIDATION NO. METHOD
THE BASIC PRINCIPLE OF THIS METHOD IS THAT DURING REDOX REATION TOTAL
INCREASE IN OXIDATION NO. MUST BE EQUAL TO THE TOTAL DECREASE IN
OXIDATION NO.
(1) INDIATE THE O.N. OF ATOM WHICH UNDERGO IN OXIDATION.
(2) CALCULATE THE TOTAL INCREASE AND DECEASE IN OXIDATION NO. PER
FORMULA UNIT OF REACTANT.
(3) EQUATE INCEASE OR DECREASE IN ON BY MULTIPLING WITH SUITABLE
INTEGER .BALANCE THE ATOM WHICH UNDERGO CHANGE IN ATOM.
(4) BALANCE EQUATION WITH RESPECT TO OTHER ATOM EXCEPT H AND O
(5) BALANCE OXYGEN ATOM BY ADDING WATER MOLECULE TO THE SIDE
DEFFICIENT IN OXYGEN ATOM.
4.REDOX REACTION AND ELECTRODE PROCESSRedox reaction: those reaction which involve change in oxidation no. of interacting species.
Types of redox reaction.
Direct redox reaction: those reaction in which oxidation and reduction occur in same vessel.
Indirect redox reaction: those reaction in which oxidation and reduction occur in different vessel.
Electro chemical cell: a device in which a redox reaction is carried in directly and the decrease in
energy appear as the electrical energy.
Representation of electrochemical cell:
ANODE; ANODE ELECTROLYTE
CATHODE ELECTROLYTE,
OXIDATION HALF CELL
REDUCTION HALF CELL
 ELETRODE POTENTIAL: IT MAY BE DEFINED AS THE POTENTIAL DIFFERENE
BETWEEN THE ELECTRODE AND ITS ION IN THE SOLUTION.
 STANDARD ELETRODE POTENTIAL: ELECTRODE POTENTIAL AT STANDARD
CONDITION OF TEMP(273K) AND COCENTRATION(`1M) ,IS CALLED AS
STANDARD ELECTRODE POTENTIAL.
 TYPES OF ELECTRODE POTENTIAL.
OXIDATION POTENTIAL: LOSS OF ELECTRON
REDUCTION POTENTIAL: GAIN OF ELECTRON
STANDARD HYDROGEN ELECTODE:
IT IS THE REVERSIBLE ELECTRODE WHICH CAN ACT BOTH AS CATHODE AND
ANODE.
EMF(ELECTRO MOTIVE FORCE):
IT IS THE DIFFERENCE OF ELECTODE OF TWO HALF CELL.
EMF = E*CATHODE – E*ANODE
#SRP : IT MEASURES THE TENDENCY TO ACCEPT ELECTRON.
#SOP : IT MEASURES THE TENDENCY TO LOSE ELECTRON.
ELETRO CHEMICAL SERIES:
THE STANDARD ELECTRODE POTENTIAL (E*) OF A LARGE NO.OF ELECTRODES
ARE DETERMINED WITH RESPET TO THE STANDARD HYDROGEN ELECTRODE
ACTING AS REFERENCE ELECTRODE. THESE ARE ARRANGED IN THEIR INCREASING
ORDER OF REDUCING STRENGTH TO FORM A SERIES KNOWN AS ELECTROCHEMICAL
SERIES.
APPLICATION OF ELECTOCHEMICAL SERIES:
[1] COMPARISION OF RELATIVE REDUCING OR OXIDISING POWER.
[2] PREDICTING THE FEASIBILITY OF REDOX REACTION.
[3] PREDICTING WHETHER A METAL CAN EVOLVE HYDROGEN FROM AN ACID OR
NOT.
[4] DETERMINING THE EMF OF A CELL.
EVALUATION TOOL –
CONCEPT - CLASSICAL IDEA OF REDOX REACTION-OXIDATON
AND REDUCTION REACTION
HOME WORK –a) Identify the species undergoing oxidation and reduction
1. H2S + Cl22HCl +S
2. 3Fe3O4+ 8Al  9Fe + 4Al2O3
b) Justify that the following rections are redox reactions :
1. CuO +H2  Cu +H2O
2.2K +F2 2KF
.REMEDIAL MEASURES –
a) Assignment – 1.level -1For slow learnersIdentify the species undergoing oxidation and reduction;
1.2Na +H22NaH
2ZnO +CZn +CO
Level -2 For averageIdetify the species undergoing oxidation and reduction.
1.Fe2O3+3CO2Fe+3CO2
2.MnO2+4HCl MnCl2+Cl2 +2H2O
Level-3 For bright
Justify that the following reaction are redox reaction .
1.4BCl3+3LiAlH42B2H6+3LiCl +3AlCl3
2.4NH3 +5O2 4NO +6H2O
EVALUATION TOOLCONCEPT- OXIDATION NUMBER AND REDOX REACTION
HOME WORK 1.Assign oxidation number to the given element .
a) P in NaH2PO4
b)Mn in K2MnO4
c)Cr in K2Cr2O7
d)N in HNO3
2.Identify the substance oxidized ,reduced ,oxidizing agent , reducing
agent .
a)2AgBr +C6H6O2  2Ag + 2HBr +C6H4O2
b)N2H4 +2H2O2N2 +4H2O
REMEDIAL MEASURESAssignment –
Level-1
1.Assign oxidation number to the given element.
a)S in H2S
b)Cr in K2CrO4
c)B in NaBH4
d)S in H2S2O7
Level-2
1.Assign the oxidation number to the given element.
I in KI3 , Fe in Fe3O4 , S in H2SO5 , Cr in CrO5 ,Ca in CaOCl2
2.Suggest a list of substances where carbon can exhibit oxidation states
from -4 to +4 and -3 to +5 .
Level – 3
1.The compound AgF2 is unstable compound . However , if formed,the
compound acts as a very strong oxidizing agent . Why ?
2.HNO3 act as only an oxidizing agent ,whereas HNO2 can act as both.
Why?
EVALUATION TOOLCONCEPT- BALANCING OF REDOX REACTIONHOME WORK1.Balance the following equation by ion electron method in acidic medium.
1)Fe 2+ +Cr2O72- Fe3+ + Cr3+
2) Cr2O72- + SO32- Cr3+ +SO422.Balance the following equation by oxidation number method .
a)K2 Cr2O7 +FeSO4 +H2SO4 K2SO4 +Fe2(SO4)3 +Cr2(SO4)3 +H2O
b)P4 +NaOH +H2O PH3 +NaH2PO2
REMEDIAL MEASURES –
AssignmentLevel -1
1.Baiance the following equation by ion electron method .
1)MnO4- +I-  MnO2 +I2( In basic medium)
2)Cr2O72- +SO2 Cr3+ +SO4 2-(In acidic medium)
Level -2
1.The Mn2+ ion is unstable in solution and undergoes disproportionation to
give Mn2+ ,MnO2 and H+ ion . Write a balanced ionic equation for the
reaction.
2.Chlorine is used to purify drinking water . Exess of chlorine is harmful
.The excess of chlorine is removed by treating with sulphur dioxide . Give
a balanced equation for this type of redox change .
Level -3
1. Permanganate (vii) ion , MnO4- in basic solution oxidizes iodide ion , Ito produce molecular iodine and manganese (iv) oxide . Write a balanced
ionic equation to represent this redox reaction.
2.In Oswald process for the manufacturing of nitric acid the first step
involves the oxidation of ammonia gas by oxygen gas to give nitric acid
and steam . What is maximum weight of nitric oxide that can be obtained
starting with 10.0gm of ammonia and 20.0gm of oxygen.
PROJECT-1.Prepare a chart representing galvanic cell .
2.Identify the different oxidation process in your daily life and write the
advantages and disadvantages of these processes .
3.Calculate the concentration of oxalate ion in guava extract by titrating
with standard KMnO4 solution .
REFERENCES1. N.C.E.R.T. Text book
2. Modern A B C of chemistry