Transcript
Redox Reaction a reaction where both
oxidation & reduction occurs at the same time.
Credits
• Chem Notes • http://www.chemguide.co.uk/inorganic/redox
/oxidnstates.html
• Xinle, jengsuan , angeline , shiyun 4E1
Reducing ?Oxidizing ?
:Reducing Agent Reduces others, but itself is being oxidized.
Oxidizing Agent : Oxidizes others, but itself is being reduced.
Reduction & Oxidation
DEFINITION OXIDATION REDUCTION
#1 0XYGEN TRANSFER Gain Oxygen (+) Lose Oxygen (-)
#2 HYDROGEN TRANSFER
Lose Hydrogen (-) Gain Hydrogen(-)
#3 ELECTRON TRANSFER
Lose Electron (-)
Gain Electron(+)
#4 OXIDATION STATE Increase (+) Decrease (-)
Oxygen Transfer Oxidizing:Gains O Reducing: Loses O
Oxygen Transfer
•CuO + H2 -> Cu + H2O
• oxidizing agent-Oxygen • reducing agent Hydrogen• Note: Oxidising & Reducing agents only
refer to reactants.
Gains O₂
Loses O₂
HYDROGEN TRANSFER Oxidation: loses H Reduction Gains H
Hydrogen Transfer
•H2S + Cl2 -> S + 2HCl
• .
• Oxidizing Agent Cloride,Cl₂• Reducing Agent Hydrogen Sulfur , H₂S
Loses H
Gains H
Electron TransferOxidation: Loses E¯Reduction: Gains E¯
Electron transfer
Oxidised ? ALUMINIUM Reduced? OXYGEN
Oxidation stateThe 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) .
RULES EXAMPLES OXIDATION STATE
1. The oxidation state of an elements in the uncombined state (free state) is zero.
Sodium (Na)Carbon ( C ) Magnesium ( Mg )Oxygen (O2)
0000
2. The oxidation state of a simple ion is equal to the charge on the ion.
Na+
Fe3+
O2-
P3-
+1 +3-2-3
3.The Oxidation states of group I and II elements in their compounds are fixed.
ALL group I and group II elements.
Group 1: +1
Group 2: +2
4. The oxidation states of hydrogen and oxygen in their compound are fixed.
* H2O2 is the only exception where the O.S of oxygen is -1
H ( in H2 O )
O ( in CuO )
+1
-2
• 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
(+2) (+3)
2FeCl2 (s) + Cl2 (g) 2FeCl3•
(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- .
oxidation ----increase in oxidation state
REDUCTION----decrease in oxidation state
Example:
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
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