1. Redox Reactions :
Summary
~ Combination of OXIDATION and REDUCTION
~ Definitions :
1.In Terms of Electrons 2.In Terms of Oxidation State
- OiL RiG
In
Oxidation
State
~ Oxidation
~ Reduction
- Oxidation State - Electronegativity Nuclear Charge
Size of Atom
}
Balancing Chemical Equations :
- Disproportionation - FON
- ION-ELECTRON Method
- OXIDATION-STATE Method
INCREASE
DECREASE}
- Central atom - Add e - Add H1+ OR 1-OH - Add H2O
- Find Oxidation State - Find Change - Cross Multiply
- Balance H & O
2 3 4 5 6 7 8 9 10 11 12 13
2. Redox Reactions
~ Redox
- RED
- OX
~ Reduction
~ Oxidation}
Simultaneously
Definitions :
In Terms of Electrons
In Terms of Oxidation State
In Terms of Electrons :
~ Oxidation ~ Reduction
Loss of e1- Gain of e1-
OiL RiG
Examples :
Al2O3 Al O
Al
Al +
+
+
+
Al3+
Al3+
3e1-
O2 4e1-
O2-
2
O2 O2-
(
) ( )
4 X
3 X
4 3 4 6
}
Al2O3
~ MgF2
1
.
.
. .
. .
.
.
.
Mg 2e1- + Mg2+
F2 + 2e1- 2F1-
Mg + F2 Mg2+ + 2 F1-
Redox Reactions Lecture- 1
AS Level
Chemistry
3. ~Mg3N2
In Terms of Electrons :
~Na2O
Na 1e1- + Na1+
O2 + 4e1-
2O2-
4 Na + O2 4 Na1+ +2 O2-
(
)
4 X
Mg
3Mg +
+
+
+
Mg2+
3Mg2+
2e1-
N2 6e1-
N3-
2
N2 2N3-
(
) ( )
3 X
Redox Reactions Lecture- 1
AS Level
Chemistry
4. In Terms of Oxidation State :
~ Oxidation ~ Reduction
INCREASE
in
Oxidation
State
DECREASE
in
Oxidation
State
IMPORTANCE
-Ionic & Covalent
-To decide redox
reactions easily
-To work-out
Calculations
easily
2
- Oxidation State / Oxidation Number
~ Charge written on AN Atom
- Electronegativity
Nuclear Charge
Size of Atom
- MORE
- MORE
- SMALL
HIGHLY
ELECTRONEGATIVE
ELEMENTS
F
O
N
1
2
3
Redox Reactions Lecture- 2
AS Level
Chemistry
5. Across the Period
Down the Group
~ Electronegativity INCREASES
~ Electronegativity DECREASES
- Nuclear Charge Increases
- Radius Increases
6. N2
0
Na
0
Cu
0
H F
1-
1+
H2 S O4
2-
1+ 6+
H2 S O4
1 x 2 + S + ( -2 x 4 ) = 0
2 + S -8 = 0
S -6 = 0
S = + 6
H N O3
2-
1+ 5+
P O4
3-
( )
2-
5+
Cr2 O7
2-
( )
6+ 2-
Mn O4
1-
( )
7+ 2-
~ OF2
~ NaH
~ NCl3
~ PCl5
~ NH3
~ CO
- Challenge YOURSELF
H2O2
O
.
. .
.
.
.
O
.
. .
.
.
. x
x H
H
1-
1- 1+
1+ CH3OH C
H
H
H
O H
1+
2-
2-
1+
1+
1+
- BaO - CH4 - BaO2 - CCl4 - CH2Cl2 - N2H4 - NH2OH
Redox Reactions Lecture- 2
AS Level
Chemistry
7. - Questions :
C + 2 H2 S O4 C O2 + 2 S O2 + 2H2 O
0 1+6+2- 4+ 2- 4+ 2- 1+ 2-
- CARBON
~ Oxidation , Since Oxidation State INCREASES from 0 to 4+
- SULFUR
~ Reduction , Since Oxidation State DECREASES from 6+ to 4+
Reducing Agent / Reductant
Oxidising Agent / Oxidant
- KI – SO2
- KMnO4 – K2Cr2O7
1
Redox Reactions Lecture- 3
AS Level
Chemistry In Terms of Oxidation State
8. 2 N H3 + 3 Cu O N2 + 3 Cu + 3 H2 O
- Questions :
3- 1+ 2+ 2- 0 0 1+ 2-
Pb O2 + 4 H Cl Pb Cl2 + Cl2 + 2 H2 O
2
3
4 Cl2 + H2 O H Cl + H O Cl
5 3 Br2 + 6 Na O H 5 Na Br + Na Br O3 + 3 H2 O
4+ 2- 1+ 1- 2+1- 0 1+ 2-
0 1+ 2- 1+1- 1+2-1+
0 1+2-1+ 1+1- 1+5+2- 1+2-
- Disproportionation
Cu2O + H2SO4 Cu + CuSO4 + H2O
Redox Reactions Lecture- 3
AS Level
Chemistry
9. Balancing Chemical Equations :
- ION-ELECTRON Method
- OXIDATION-STATE Method
~ IONIC Equations
1 ION-ELECTRON Method :
~ IONIC & MOLECULAR
Equations
RULES
1- Balance the Central atom
2- Balance Oxygen by adding water
3- Balance Hydrogen by adding H1+
4- Balance Charge by adding e
Fe 2+ Fe3+ + 1e 1-
MnO4
1- Mn2+
+ 5e1-
+
8H1+ + 4H2O
Cr2O7
2-
Cr3+
+ 6e1- + 14 H1+
+ 7H2O
2
10. NO2
1-
1 ION-ELECTRON Method :
NO3
1-
+ 2e 1- + 2H 1+
+ H2O
- Questions :
1.The Oxidation of Cr(OH)3 to CrO4
2- in
Alkaline Solution
Cr(OH)3 CrO4
2- + 3 e 1-
+ 5 1- OH + 4 H2O
2.The Reduction of VO2
1+ to V 2+ in Acid Solution
VO2
1+ V2+
+ 3e1- + 4 H 1+ + 2 H2O
The Oxidation of H2C2O4 to CO2 in Acid Solution
3.
+ 2 H 1+
H2C2O4 CO2 + 2 e 1-
4. The Reduction of IO3
1- to I2 in Acid Solution
IO3
1- + 6 H2O
I2
2 + 10 e1- + 12 H1+
2
11. - Questions :
1 ION-ELECTRON Method :
5. The Reduction of O2 in Alkaline Solution
O2
1-OH
+ 4 e 1- + 2 H2O 2
4
The Reduction of H2O2 to Water in Acid Solution
6.
H2O
H2O2 + 2 e 1-+ 2 H1+
The Oxidation of H2O2 to Oxygen in Alkaline
Solution
7.
+ 2 H2O
H2O2 + 2 1- OH O2 + 2 e 1-
Fe 2+ Fe3+ + 1e 1-
MnO4
1- Mn2+
+ 5e1-
+
8H1+ + 4H2O
~ Complete REDOX Equations
( )
2
X 5
5 Fe 2+ + MnO4
1- + 8 H1+ Mn2+ + 5 Fe3+ + 4 H2O
Redox ~ Balancing equations `Slide 9
2 3 4 5 6 7 8 10 11 12 13 BTS
12. ~ Complete REDOX Equations
8. The Oxidation of NO2
1- to NO3
1-with
Manganate (VII) ions, MnO4
1- in Acid Solution
The Reduction of Iodate (V)IO3
1- to Iodine , I2 ,by
Iodide ions, I 1- in Acid Solution
9.
MnO4
1- Mn2+
+ 5e1-
+
8H1+ + 4H2O
NO2
1- + H2O NO3
1- + 2 e 1- + 2 H 1+
(
)
(
)
X 5
X 2
5 NO2
1- + 6 H 1+ + 2 MnO4
1- 5 NO3
1- + 2 Mn 2+ + 3 H2O
2 IO3
1- + 10 e 1- + 12 H 1+ I2 + 6 H2O
2I1- I2 + 2 e 1-
(
)
5 X
10 I 1- + 2 IO3
1- + 12 H 1+ 6 I2 + 6 H2O
Redox ~ Balancing equations `Slide 10
2 3 4 5 6 7 8 9 11 12 13 BTS
13. OXIDATION STATE Method :
2
RULES
1- Identify the elements with Different Oxidation state
2- Deduce the change in oxidation state
3- Cross Multiply the Change
4 - Balance Other Elements like Hydrogen & Oxygen
…. Fe 2+ +….MnO4
1- +….H1+ ….Mn2+ + ….Fe3+ + …. H2O
1
5 5
1 4
8
2+ 3+
7+ 2+
( 1 ) ( 5 )
…. Fe 2+ +….MnO4
1- +….H1+ ….Mn2+ + ….Fe3+ + …. H2O
1
5 5
1 4
8
Redox ~ Balancing equations `Slide 11
2 3 4 5 6 7 8 9 10 12 13 BTS
