Unit 10' OxidationReduction Chemistry Recommended Problems

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Unit 10. Oxidation-Reduction Chemistry
Recommended Problems

• Oxidation and Reduction are opposites Cant
  have one without the other.
• Self-test A 1, 3, 6-9
• Self-test B 1-3
• Self-test C 1-4, 6, 7
• Self-test D 1, 3, 5, 6, 9

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Redox in Your Life
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• Rusting of you car
• Heating your home in winter
• Batteries

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Oxidation - the Gain of Oxygen Reduction - the
Loss of Oxygen
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• CH4 2 O2 ----gt CO2 2 H2O
• 4 Fe 3 O2 ----gt 2 Fe2O3
• CuSO4 Zn ----gt Cu ZnSO4

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Oxidation - the Loss of Hydrogen Reduction - the
Gain of Hydrogen
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• CH4(g) 2 O2(g) ----gt CO2(g) 2 H2O(g)
• 4 Fe 3 O2 ----gt 2 Fe2O3
• CuSO4 Zn ----gt Cu ZnSO4

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How do We Reconcile the Discrepancies?
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• Oxidation State- the charge that develops on an
  atom in order to satisfy the octet rule.

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Oxidation is the Loss of Electrons Reduction is
the Gain of Electrons
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• Mnemonic device OIL RIG

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Rules for Determining Oxidation State
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• 1. Elemental atoms have oxidation state of zero.
• Elemental atoms- atoms that are uncombined with
  atoms of other elements.
• 2. Main group elements have the expected
  oxidation state.
• 3. Calculate oxidation state of transition
  elements and group IVA elements.
• 4. The sum of charges on a molecule must equal
  0 must equal the charge of polyatomic ions.

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Sample Test Questions
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• 1. Determine the oxidation state of carbon in the
  following molecules CH4, CO, CO2
• 2. Determine the oxidation state of the
  underlined atom in the following molecules
• FeCl2, FeCl3, Fe(NO3)2, Fe3(PO4)2

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Definitions
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• Oxidizing agent- reactant molecule which oxidizes
  an atom of another element in a reaction. Since
  redox reactions occur only in pairs, the
  oxidizing agent contains the reduced element.
• Reducing agent- reactant molecule which reduces
  an atom of another element in a reaction. The
  reducing agent contains the oxidized element.

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Sample Test Questions
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• 1. In the reaction, Fe2O3 3 C ----gt 2 Fe
  3CO, identify a) the element that is
  oxidized b) the element that is reduced c)
  what the oxidizing agent is d) what the
  reducing agent is
• 2. In the reaction, C2H4 H2 ----gt C2H6,
  identify a) the element that is oxidized b)
  the element that is reduced c) what the
  oxidizing agent is d) what the reducing agent
  is

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Activity Series (Table 10.6)
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• F2 2 e ----gt 2 F
• Cl2 2 e ----gt 2 Cl
• O2 4 e 4H ----gt 2 H2O
• Ag e ----gt Ag
• Fe3 e ----gt Fe2
• Cu2 2 e ----gt Cu
• Fe2 2 e ----gt Fe
• Zn2 2 e ----gt Zn
• Li e ----gt Li

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Sample Test Questions
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• Will Cu2 oxidize the F2?
• Predict whether the following reaction would be
  expected to occur 2 Na Fe2 ----gt 2 Na Fe

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Application of the Activity Series
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• 2 Fe ----gt 2 Fe3 3 e
• O2 2 H2O 4 e ----gt 4 OH
• 2 Fe3 6 OH ----gt Fe2O33H2O
• Galvanizing- coating of iron with Zinc
• Fe2 Zn ----gt Fe Zn2
• 2 Zn3 6 OH ----gt Zn2O33H2O

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Batteries
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• There are a lot of different kinds of batteries
• Be sure to read .
• Primary battery- (nonrechargable) the redox
  reaction cannot be reversed.
• Rechargable battery- chemical and electrical
  energy can be converted back and forth.

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Electrochemical Cells and Batteries
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One Example The NiCad Battery
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Ox rxn Cd (s) 2 OH (aq) -----gt Cd(OH)2 (s)
2 e Red rxn NiO2 (s) 2 H2O 2e ----gt
Ni(OH)2 (s) 2 OH (aq)
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Sample Test Questions
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• The following reaction is one of two that occurs
  in a battery. At which electrode does this
  reaction take place? MnO2 H2O ----gt MnO(OH)
  OH

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Electrolysis
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• Used often to purify chemicals H2, O2, Cu, Al,
  Fe

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Electrolysis of Water
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Electrolysis of Metal Ores (Al, Fe)
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Electroplating
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Au2 2e ----gt Au