REDOX

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REDOX

• Oxidation-Reduction Reactions

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Oxidation-Reduction Reactions

• Electrons transferred 1 atom to another
• Redox reactions
• All single-replacement rxns
• All combustion rxns

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LEO GOES GER!!!
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Oxidation

• loss of electrons
• LOSS of ELECTRONS OXIDATION
• LEO

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Reduction

• gain of electrons
• GAIN of ELECTRONS REDUCTION
• GER

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REDOX

• Oxidation Reduction complementary reactions
• occur together simultaneously or not at all

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Oxidation Numbers

• In Ionic Compounds
• of electrons lost/gained by atom determined by
  ions that form compound

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Assigning Oxidation Numbers
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Rule 1 of free, uncombined element 0
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Rule 2
of monatomic ion charge of ion
Ca2 2 Cl-1 -1 Al3
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Remember Ions form ionic cmpds
CaCl2, Al(NO3)3, etc.
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• Rule 3
• F always -1

CF4
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• Rule 4
• H is nearly always 1
• except if bonded to metal then -1

H2O, HNO3, H2SO4, LiH, CaH2, NaH
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O is nearly always -2 except when
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Rule 6 Sum oxidation in neutral
compound 0
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Rule 7 Sum oxidation in polyatomic ion
charge of ion
Sum in SO4-2 -2 Sum in NO3-1 -1
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Rule 8 Covalent cmpds oxidation more
electronegative atom negative charge if
was ion NH3 N -3, H 1 SiCl4 Si 4,
Cl -1
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Assign Oxidation Nos

• KCl
• CaBr2
• CO
• CO2
• Al(NO3)3
• Na3PO4
• H2S
• NH41
• SO3-2

Ca 2, Br -1
C 2, O -2
C 4, O -2
Na 1, O -2, P 5
H 1, S -2
N -3, H 1
S 4, O -2
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4 3 2 1 0 -1 -2 -3 -4
2) And if youre lucky you strike oil it
shoots up
1) You dig down with an oil rig
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Electrons are Negative!

• Why use the word reduced when electrons are
  gained?

• Look at how the oxidation number changes
• Ex Cl gains an electron ? Cl-1
• oxidation ? from 0 to -1 the was reduced

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Writing Equations

• Even though oxidation reduction reactions occur
  together we write separate equations for each
  process
• known as Half-Reactions

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Reduction Half-Reactions

• I2 2e- ? 2I-1
• O2 4e- ? 2O-2
• Half-reactions must demonstrate
• conservation of mass conservation of charge
• atoms on left must atoms on right
• total charge on left must total charge on right

Electrons are gained so put on reactant
side!
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Oxidation Half-reactions
Electrons are lost so they are put on product
side!

• K ? K1 1e-
• Fe2 ? Fe3 1e-
• Cu ? Cu2 2e-
• Total Charge on left Total Charge on right
• atoms on left atoms on right

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Vocabulary Interlude

• Oxidizing Agent Substance being reduced
• Accepts electrons from something else
• aids oxidation for another species
• Reducing Agent Substance being oxidized
• Loses electrons to something else
• aids reduction for another species