oxidation and reduction reactions magda van aardt university senior college...
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![Page 1: Oxidation and Reduction Reactions Magda van Aardt University Senior College Murray.thompson@adelaide.edu.au Dr Tak Kee Department of Chemistry University](https://reader034.vdocuments.site/reader034/viewer/2022051115/56649e905503460f94b94269/html5/thumbnails/1.jpg)
Oxidation and Reduction Reactions
Magda van AardtUniversity Senior [email protected]
Dr Tak KeeDepartment of ChemistryUniversity of Adelaide
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“This material has been developed as a part of the Australian School Innovation in Science, Technology and Mathematics Project funded by the Australian Government Department of Education, Science and Training as a part of the Boosting Innovation in Science, Technology and Mathematics Teaching (BISTMT) Programme.”
Oxidation and Reduction Reactions
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•When light travels from one medium to another it changes speed.
•It also changes direction.
Refraction and Optical Fibres
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Oxidation and Reduction Redox Reactions
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Chemical reaction types
Acid-base reactions & double replacement reactions
Redox reactions can be Redox reactions can be :: * Single replacement reaction* Single replacement reaction
* Combination reactions * Combination reactions
* Decomposition * Decomposition * Combustion reactions* Combustion reactions
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Redox Reactions
Involve a transfer of electrons between reacting species. …
Takes place when reduction and oxidation occur simultaneously
RED + OX = REDOX
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Redox reactions in batteries
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h
Redox reactions in lead acid batteries
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Redox reactions in photosynthesis
http://plantsandalgae/photography_091.jpeg
6H2O + 6CO2
+ light energy →
C6H12O6 + 6O2
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Cell respiration Cell respiration
→ Energy = ATP
(adenosine triphosphate
)Glucose
http://biology.clc.uc.edu/Courses/bio104/cellresp.htm
C6H12O6 + 6O2
→
6CO2 + 6H2O + 30ATPenergy
+ + +Glucose =reductant Oxygen
=oxidant
Carbon dioxide
water
ATP
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Photography
K2Cr2O
7
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Electrolysis of water
2 H2O(l) → O2(g) + 2H2(g)
Electrolysis: Electrolysis: SALTS AND WATER SALTS AND WATER
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Oxidation half equation: H2 (g) → 2H+ + 2e-
http://p2library.nfesc.navy.mil/issues/emergeoct2005/fuelcell.jpg
Reduction at Cathode
Oxidation at the anode
Fuel Cells
Reduction half equation:½O2 (g)+ 2e- + 2H+ → H2O
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Space Shuttle Discovery hurtles into space on missionSTS-105, August 10, 2001.
Fuel Cells (cont)
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Complete Combustion of propane:
C3H8( g) + O2 (g) → 3CO2(g) + 4H2O(g)
Combustion
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FireworksFireworks
http://www.chemsoc.org/ExemplarChem/entries/2004/icl_Gondhia/lightcolour.htmlComposition
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http://commons.wikimedia.org/wiki/Image:Bleach-bottle.jpg
REDOX REACTIONS IN REDOX REACTIONS IN BLEACHES: BLEACHES: HH22OO22 HClOHClO SOSO22
http://www.ultrasonic-stain-remover.com/blood_stain_remover.jpger.com/blood_stain_remover.jpg
http://www.npr.org/templates/story/story.php?storyId=3892457
HOCl (aq) is the active ingredient in White King
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Rusting / corrosion
Rust = Fe2O3.H2O (the red brown flaky stuff)
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reduction
Fe2O3 (S) + CO (g) → 2Fe (l) + 3CO2 (g)
+3 +2 0 +4
oxidation
Steel making (cont)
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Steel making (cont)
Fe2O3 (s) + 3CO (g) → 2Fe (s) + 3CO2
http://www.bbc.co.uk/history/interactive/animations/blast_furnace/index.shtml
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Galvanic Cells Galvanic Cells
Salt bridge = Electrolyte = Solution with ions to carry charge KCl (aq) or NO3(aq)
ELECTROLYTES
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http://www.glenair.com/qwikconnect/vol7num4/electro.jpg
Electroplating
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Spin-Coating – a simple way to produce thin films
Films of ~100 nm can be routinely produced
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2424
Tris(2,2'-bipyridyl) Ruthenium(II)
+ –
Voltage sourceV volts
+ –
Field line
Positive charge or hole migration
Electron migration
Device material (Ru2+)
Organic Light Emitting Diode (OLED)
Electron (in the form of Ru+) and hole (Ru3+) migrate towards centre and recombine to produce light – A 3rd year Chem student practical at Adelaide University
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LESSON 2 LESSON 2
OXIDATION AND REDUCTIONOXIDATION AND REDUCTION
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REDOX = OXidation + REDuction
What is oxidation ?What is oxidation ?
What is What is reduction? reduction?
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OXIDATION IS DEFINED AS :
1: LOSS OF HYDROGEN CH3 OH Cr2O7 2-
→ CH2O
(methanol) H+ (heat) (methanal)
What is oxidation?
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OXIDATION IS DEFINED AS :
2: GAIN OF 2: GAIN OF OXYGENOXYGEN
MgMg(s) (s) + O+ O2(g) 2(g) → 2MgO→ 2MgO
2Ca 2Ca (s)(s) + + OO2(g) 2(g) → 2CaO→ 2CaO
What is oxidation?
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OXIDATIONOXIDATION ISIS DEFINED AS :DEFINED AS :
3:LOSS OF ELECTRONS =OXIDATION (LEO)
What is oxidation?
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OXIDATIONOXIDATION ISIS DEFINED AS :DEFINED AS :
4: INCREASE IN OXIDATION NUMBER
Fe (s) → Fe 2+ (aq) + 2e-
0 +2
What is oxidation?
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REDUCTIONREDUCTION ISIS DEFINED AS :DEFINED AS :
1: GAIN OF HYDROGEN C3H6 (g) + H2(g) (catalyst) Ni → C3H8(g) (propene) heat pressure (propane)
What is reduction?
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2: LOSS OF 2: LOSS OF OXYGENOXYGEN
CuO (s) + H2(g) → Cu (s) + H2O (g)
REDUCTIONREDUCTION ISIS DEFINED AS :DEFINED AS :
What is reduction?
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3:3: GAIN OF ELECTRONS GAIN OF ELECTRONS
=REDUCTION=REDUCTION
(GER)(GER)
O2(g) + 4e- → 2O2- (aq)
REDUCTIONREDUCTION ISIS DEFINED AS :DEFINED AS :
What is reduction?
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4: DECREASE IN OXIDATION NUMBER
Cl2 (g) + 2e- → 2Cl-(aq)
0 -1
REDUCTIONREDUCTION ISIS DEFINED AS :DEFINED AS :
What is reduction?
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When is it a redox reaction ? When is it a redox reaction ?
What about this reduction reaction? What about this reduction reaction?
2MnO2MnO44--(aq)(aq)+ 16H+ 16H+ + +10e+10e-- → Mn → Mn2+2+
(aq)(aq)+ 8H+ 8H22OO(l)(l)
and this one?and this one?
CrCr22OO772-2-
(aq) (aq) ++ 14H14H++ +6e+6e- - → 2Cr→ 2Cr3+3+
(aq)(aq)+ 7H+ 7H22OO(l)(l)
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uncombined with other uncombined with other elements their elements their oxidation number isoxidation number is
ELEMENTS:
ZERO
H2 Li N2 O3 S8 Fe Cu Mg Cl2 O2 F2
Rule1
Rules to determine oxidation numbers
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SIMPLE IONS:
RULE 2
their oxidation number their oxidation number is the charge on the ion : is the charge on the ion :
H+
=+1 Fe2+ = +2
O2- = -2 Al 3+ = +3
Rules to determine oxidation numbers
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OXYGEN: IN COMPOUNDS IS –2
[except in hydrogen peroxide (H2O2 )it is -1 compounds in which it is bounded to fluorine F2O it is +2 ]
SO2
Na2O CO
P4O10
K2CO3 MgSO4
Rules to determine oxidation numbers
RULE 3
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MOLECULES:
THE SUM OF THE OXIDATION NUMBERS IS:
ZERO
What is the oxidation number of Phosphorus (P) in P4 O10
4(Phosphorus ‘s oxidation number which we will take as x ) + 10( oxidation number of oxygen) = 0 4 X + 10 (-2) = 0 4 X = 20 X = +5 X= +IV
YOU TRY : S in SO3… and Cl in HClO
Rules to determine oxidation numbers
RULE 2
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HYDROGEN:
= +1 when in compound with a non metal
NH3
AMMONIA
H2OWATER
HClHYDROCHLORIC ACID
NH4+
AMMONIUM
Rules to determine oxidation numbers
RULE 5
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COMPLEX / POLYATOMIC IONS:
CHARGE ON THE ION
THE SUM OF ALL THE OXIDATION
NUMBERS IS:
What is the oxidation number of S in SO42- ?
(oxidation number of S is x)
SO42-
x + 4 (-2) = -2
x -8 = -2
x= +8-2
x=+6
Rules to determine oxidation numbers
RULE 6
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Is HIs H2(g) 2(g) + I+ I2(g) 2(g) → 2HI → 2HI (g) (g) a redox reaction?a redox reaction?
The oxidation number of hydrogen changes from 0 to +I Increase in oxidation number Hydrogen has been oxidised (undergoes oxidation) Hydrogen is the reductant (reducing agent)
0Rule 1
+1Rule 5
Using oxidation numbers to identify a redox reaction
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The oxidation number of iodine changes from 0 to – I Decrease in oxidation number Iodine has been reduced (undergoes reduction)Iodine acts as the oxidant (oxidising agent)
The oxidation number of iodine changes from 0 to – I Decrease in oxidation number Iodine has been reduced (undergoes reduction)Iodine acts as the oxidant (oxidising agent)
Is HIs H2(g) 2(g) + I+ I2(g) 2(g) → 2HI → 2HI (g) (g) a redox reaction?a redox reaction?
-1 Rule 4 and 5
0Rule 1
Using oxidation numbers to identify a redox reaction
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0Rule 1
+1Rule 5
-1 Rule 4+5
0Rule 1
Is HIs H2(g) 2(g) + I+ I2(g) 2(g) → 2HI → 2HI (g) (g) a redox a redox
reaction?reaction?
Yes, oxidation number has changed for different chemical species
Using oxidation numbers to identify a redox reaction
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2)2) MgMg(s) (s) + H+ H22SOSO4 (aq) 4 (aq) → MgSO→ MgSO4 (aq) 4 (aq) + H+ H2 (g) 2 (g)
0 Rule 1
+1Rule
5+2
0 0
-2-2+6 +6
The oxidation number of magnesium changes from 0 to +2 Increase in oxidation number Magnesium metal has been oxidised (undergoes oxidation) Magnesium metal (Mg) is the reductant (reducing agent)
The oxidation number of H (in H2SO4 changes from +1 to 0 (in H2)Decrease in oxidation number H2SO4 has been reduced (undergoes reduction)H2SO4 acts as the oxidant (oxidising agent)
The oxidation number of H (in H2SO4 changes from +1 to 0 (in H2)Decrease in oxidation number H2SO4 has been reduced (undergoes reduction)H2SO4 acts as the oxidant (oxidising agent)
Using oxidation numbers to identify a redox reaction