Electrochemistry

1
Electrochemistry

• REDOX

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Oxidation and Reduction

• Oxidation is the process by which a substance
  loses one or more electrons.
• Reduction is the process by which a substance
  gains one or more electrons.
• Because oxidation and reduction occur together,
  reactions in which electrons are transferred
  between reactants are called oxidation-reduction
  reactions, or simply redox reactions.

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What is the oxidation number of each element?

• K2Cr2O7
• SO2
• Al(NO3)3
• K2SO4
• H2SO4

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Oxidizing and Reducing Agents

• An oxidizing agent causes the oxidation of
  another substance by accepting electrons from
  that substance.
• The oxidizing agent contains the atom that shows
  a decrease in oxidation number.
• The oxidizing agent is reduced.
• A reducing agent causes reduction by providing
  electrons to another substance.
• Shows an increase in oxidation number.

5
ExamplesIdentify which is oxidized and which is
reduced. Identify the oxidizing and reducing
agents.

• Cu 2AgNO3 Cu(NO3)2 2Ag
• 3H2S 2HNO3 3S 2NO 4H2O
• Zn CuCl2 ZnCl2 Cu
• C 2Cl2 CCl4
• H2 Cl2 2HCl

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Voltaic Cells

• Produces electrical energy from chemical energy
• flow of electrons is the result of a spontaneous
  redox reaction
• for any two metals in the activity table, the
  metal that is higher is the more readily oxidized

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Electrolytic Cells electrolysis is carried out
to bring about a chemical change electrons are
pushed by an outside power source example
electrolysis of water produces hydrogen gas
and oxygen gas Applications electrowinding ele
ctroplating electrorefinishing
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Standard Reduction Potentials a positive
standard potential is SPONTANEOUS a negative
standard potential is NONSPONTANEOUS Maximum
Voltage look at the table standard reduction
potentials higher voltage - lower voltage
maximum voltage be careful when subtracting
negative numbers!