1. Redox Reaction
a reaction where both oxidation & reduction
occurs at the same time.

2. Credits
• Chem Notes
• http://www.chemguide.co.uk/inorganic/redox
/oxidnstates.html
• Xinle, jengsuan , angeline , shiyun 4E1

3. Reducing ?Oxidizing ?

4. :Reducing Agent Reduces others, but
itself is being oxidized.
Oxidizing Agent : Oxidizes others,
but itself is being reduced.

5. Reduction & Oxidation
DEFINITION OXIDATION REDUCTION
#1 0XYGEN TRANSFER Gain Oxygen (+) Lose Oxygen (-)
#2 HYDROGEN Lose Hydrogen (-) Gain Hydrogen(-)
TRANSFER
#3 ELECTRON Lose Electron Gain Electron(+)
TRANSFER (-)
#4 OXIDATION STATE Increase (+) Decrease (-)

6. Oxygen Transfer
Oxidizing:Gains O
Reducing: Loses O

7. Oxygen Transfer
Gains O₂
• CuO + H2 -> Cu + H2O
Loses O₂
• oxidizing agent-Oxygen
• reducing agent Hydrogen
• Note: Oxidising & Reducing agents only refer to reactants.

8. HYDROGEN
TRANSFER
Oxidation: loses H
Reduction Gains H

9. Hydrogen Transfer
Loses H
•H2S + Cl2 -> S + 2HCl
• . Gains H
• Oxidizing Agent Cloride,Cl₂
• Reducing Agent Hydrogen Sulfur , H₂S

10. Electron Transfer
Oxidation: Loses E¯
Reduction: Gains E¯

11. Electron transfer
Oxidised ? ALUMINIUM
Reduced? OXYGEN

12. Oxidation state
The oxidation state is the charge and atom of an ion in a compound.
A.K.A oxidation number. OS
Either a positive number(+) or a negative number(-) or zero(0) .

13. RULES EXAMPLES OXIDATION STATE
1. The oxidation state of an Sodium (Na) 0
elements in the uncombined state Carbon ( C ) 0
(free state) is zero. Magnesium ( Mg ) 0
Oxygen (O2) 0
2. The oxidation state of a simple Na+ +1
ion is equal to the charge on the Fe3+ +3
ion. O2- -2
P3- -3
3.The Oxidation states of group I ALL group I and group II elements. Group 1: +1
and II elements in their compounds
are fixed. Group 2: +2
4. The oxidation states of hydrogen H ( in H2 O ) +1
and oxygen in their compound are
fixed. O ( in CuO ) -2
* H2O2 is the only exception where
the O.S of oxygen is -1

14. • Oxidation occurs when the O.S of an element
increases (+)
• Reduction occurs when the O.S of an element
decreases (-)
!Oxidation and reduction always occur together

15. Example: oxidation ----increase in oxidation
state
(+2) (+3)
2FeCl2 (s) + Cl2 (g)  2FeCl3
•
REDUCTION----decrease in oxidation
state
(a)Oxidation state of Iron increases from +2 in
FeCl2 to +3 in 2FeCl3 .
(b)Oxidation state of Chlorine decreases from 0 in
Cl2 to -1 in Cl- .

16. Question
• (NH4)2SO4
since (NH4) has a oxidation state of +1 , (NH4)2 = +2
Oxidation state of nitrogen in (NH4)2 is N2 + 8(+1)= 2(+1)
N2 = +2 -8
N2 = -6
N = -3
Oxidation state of hydrogen in (NH4)2 = +1
since SO4 an oxidation state of -2 ,
oxidation state of sulfur in SO4 is S +4(-2)=-2
S= -2+8
S =+6
Oxidation state of oxygen in SO4 is -2