CONTENT : CONTENT SIMPLE CONCEPT OF OXIDATION-REDUCTION
EXAMPLES OF OXIDATION
ELECTRONIC CONCEPT OF OXIDATION-REDUCTION
EXAMPLES OF OXIDATION (electronic concept)
EXAMPLES OF REDUCTION (electronic concept)
OXIDISING AND REDUCING AGENT
CATAGORIES OF OXIDATION AND REDUCTION REACTION.
OXIDATION REDUCTION OCCURS SIMULTENIOUSLY
OXIDATION NUMBERS
TEST YOYRSELF
Slide 2 : REDOX REACTION OH…HO…HO…WHAT A JOKE !!
Redox means Oxidation-Reduction : Redox means Oxidation-Reduction
Slide 4 : Oxidation-Reduction can be explained by
Slide 5 : Oxidation is known as addition of oxygen with
a substance or removal of hydrogen from a
substance. SIMPLE CONCEPT OF OXIDATION-REDUCTION
Slide 6 : Reduction is known as addition of hydrogen
with a substance or removal of oxygen from a substance. SIMPLE CONCEPT OF OXIDATION-REDUCTION
Slide 7 : EXAMPLES OF OXIDATION Oxidation process 1. 2Mg + O2 2MgO
Slide 8 : ELECTRONIC CONCEPT OF OXIDATION-REDUCTION An oxidation-reduction reaction
involves the transfer of electrons .
LEO growls GER : LEO growls GER Losing Electrons Oxidation Gaining Electrons Reduction
Slide 10 : When an atom or ion LOOSE electrons is called oxidation reaction. OXIDATION Electron loosing REDUCTION When an atom or ion GAIN electrons is called reduction reaction. Electron gaining
Slide 11 : EXAMPLES OF OXIDATION Atom looses electron “ “ “ Ion looses electron
Slide 12 : EXAMPLES OF REDUCTION 1. Cl + e Cl- 2. S + 2e S-- 4. Cu+2 + e Cu+ 5. Fe+2 + 2e Fe 3. Fe+++ + e Fe++ Atom gains electron “ “ “ Ion gains electron
Slide 13 : Oxidising agents are themselves reduced. They oxidise the other reactant. OXIDISING AND REDUCING AGENT Reducing agents are themselves oxidized. They reduce the other reactant.
Slide 14 : The reaction of an iron nail with a solution of copper sulphate(CuSO4) produces copper and ferrous sulphate. Consider the following reaction
Slide 15 : Here Fe - 2e Fe++ Cu++ + 2e Cu Self oxidation i.e. reducing agent Self reduction i.e. oxidising agent So the net ionic reaction is Loss of two electrons Gain of two electrons So this reaction involves both oxidation and reduction. The species which looses electrons is said to be oxidized. The species which gains electrons is said to be reduced.
Slide 16 : Most oxidation-reduction reactions fall into one of the following simple categories: Combination 2. Decomposition
4. Combustion : 4. Combustion 3. Displacement
Slide 18 : During redox, one atom is oxidised while another atom is reduced. Reduction and oxidation happens together!! OXIDATION REDUCTION OCCURS SIMULTENIOUSLY See the following examples: Loss of two electrons Gain of two electrons 1. (Oxidation) (Reduction)
Slide 19 : The ionic form of the equation is 2. So oxidation and reduction occurs simultaneously.
During redox, one atom is oxidized while another atom is reduced. Reduction and oxidation happen together. : Oxidation During redox, one atom is oxidized while another atom is reduced. Reduction and oxidation happen together. The oxidation numbers of the atoms will change…. one goes up (0 to +1) and one goes down (0 to -2) 2H2 + O2 2H2O Reduction 2- +1 0 0
In a redox reaction the number of electrons lost is equal to the number of electrons gained. : In a redox reaction the number of electrons lost is equal to the number of electrons gained. The number of electrons must be balanced! 12 electrons are transferred in this reaction
Slide 22 : OXIDATION NUMBERS Rules for determining oxidation numbers. 1. The oxidation number of any free element is zero, regardless of how complex the allotrope may be. 2. The oxidation number for any simple, monatomic ion is equal to the charge of the ion.
Slide 23 : 3. The sum of all the oxidation numbers of the atoms in a molecule or polyatomic ion must be equal to the charge of the substance. 4. In its compounds, chlorine always has an oxidation number of –1. 5. In its compounds, hydrogen has an oxidation number of +1 except for hydrides, where the oxidation number is -1.
Slide 24 : 6. In its compounds, oxygen has an oxidation number of -2 except for the peroxides and superoxides, which have oxidation numbers of -1 and -1/2 respectively. Examples: Find the oxidation numbers of all of the species present in the following compounds. CuO, Na2SO4, K2Cr2O7, KMnO4, NO3- , PO43-
Slide 25 : Na2SO4
Na is +1 because it is a group 1 metal
O is -2
The oxidation number
of Sulfur must be
calculated
2(+1) + X + 4(-2) = 0
(2 ) + X + (-8) =0
X = +6 CuO
Oxygen is -2
The oxidation
number of copper
must be calculated
X + (-2) = 0
X = +2 OXIDATION NUMBER CALCULATION
Slide 26 : PO43-
Oxygen is 2-
The oxidation number
of phosphorous must
be calculated
X + 4(-2) = -3
X + (-8) = -3
X = +5 NO3-
Oxygen is 2-
The oxidation
number of nitrogen
must be calculated
X + 3(-2) = -1
X = 5+ OXIDATION NUMBER CALCULATION
Test yourself : Test yourself As a Ca atom undergoes oxidation to Ca2+ , the number of neutrons in its nucleus
(1) decreases
(2) increases
(3) remains the same þ
Test yourself : Given the reaction:
Mg(s) + 2H+(aq) Mg2+(aq) + H2(g)
Which species undergoes oxidation?
(1) Mg(s)
(2) H+(aq)
(3) Mg+2 (aq)
(4) H2 (g) þ (LEO growls GER) Test yourself
Test yourself : Given the equation:
C(s) + H2O(g) CO(g) + H2 (g)
Which species undergoes reduction?
(1) C(s)
(2) H +
(3) C2+
(4) H2 (g) þ (LEO growls GER) Test yourself
Test yourself : Test yourself
Test yourself : Given the equation:
2 Al + 3 Cu2+ 2 Al3+ + 3Cu
The reduction half-reaction is
(1) Al Al 3+ + 3e –
(2) Cu 2+ + 2e – Cu
(3) Al + 3e – Al 3+
(4) Cu 2+ Cu + 2e – þ Test yourself
Test yourself : What is the oxidation number of chromium in
K2Cr2O7 ?
+12
(2) +2
(3) +3
(4) +6 þ Test yourself
Test yourself : In which substance does chlorine have an
oxidation number of +1?
(1) Cl2
(2) HCl
(3) HClO
(4) HClO2 þ Test yourself