Redox Reactions

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Redox Reactions
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REDOX Reactions

• The simultaneous transfer of electrons between
  chemical species
• Actually 2 different reactions occurring at the
  same time
• Oxidation a loss of electrons
• Reduction a gain of electrons
• These electrons are the same and both of these
  reactions are called half reactions
• or REDUCTION/OXIDATION reaction

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OXIDATION

• Can be defined as
• The loss of electrons
• The gain of oxygen
• The loss of hydrogen

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OXIDATION

• The loss of electrons
• Na(s) ? Na e-
• The sodium ion has been oxidized to the sodium
  cation.

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OXIDATION

• Gain of oxygen
• Combustion reactions are classic examples
• C(s) O2(g) ? CO2(g) (burning of coal)
• 2Fe(s) 3O2(g) ? 2Fe2O3(s) (rusting of iron)

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OXIDATION

• Loss of hydrogen
• Oxidation can sometimes be best seen as the loss
  of hydrogen
• CH3OH(l) ? CH2O(l) H2(g)
• Methyl alcohol has been oxidized into formaldehyde

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REDUCTION

• 3 Definitions
• The gain of electrons
• The loss of oxygen
• The gain of hydrogen

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REDUCTION

• Gain of electrons
• The process of silver electroplating
• Ag e- ? Ag
• Silver cation has gained an electron and has been
  reduced to silver metal.

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REDUCTION

• Loss of oxygen
• Reduction can also be seen as the loss of oxygen
  in going from reactant to product.
• Fe2O2 (s) 3 CO (g) ? 2 Fe(s) 3 CO2(g)
• Iron ore is reduced to iron metal in a blast
  furnace with carbon monoxide

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REDUCTION

• Gain of hydrogen
• A reduction can also be described as the gain of
  hydrogen atoms going from reactant to product.
• CO(g) 2 H2(g) ? CH3OH(l)
• Carbon monoxide has been reduced to methyl alcohol

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Ones loss is anothers gain

• Neither oxidation or reduction can take place
  without the other.
• When those electrons are lost something else has
  to gain them.
• When trying to remember which is which think of
  LEO the lion goes GER
• Lose Electrons Oxidation
• Gain Electrons Reduction

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Half Reactions

• Zn(s) Cu2 ? Zn2 Cu
• This overall reaction is really composed of two
  half reactions
• Zn(s) ? Zn2 2e- (oxidation half reaction)
• Cu2 2e- ? Cu(s) (reduction half reaction)

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AGENTS

• Zn(s) Cu2 ? Zn2 Cu
• Zn is being oxidized but without Cu2 present,
  nothing will happen
• Cu2 is the oxidizing agent since it is accepting
  electrons from whatever is being oxidized.
• Cu2 is reduced as it gains electrons
• Zn is furnishing the electrons and is called the
  reducing agent

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AGENTS

• To recap
• Oxidizing agent the species thats being
  reduced
• Reducing agent the species thats being oxidized