Electrochemical

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Electrochemical ElectrolyticCells

• Using Redox Reactions in everyday life

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Uses for Redox Reaction

• Electrochemical or Voltaic Cell redox reactions
  that are utilized to produce electrical energy.
  (Ex. Batteries, fuel cells)

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Electrons flow downhill

• An electrochemical or voltaic cell can be
  compared to a hydro-electric power plant. In the
  power plant the energy of the water is harnessed
  as the water flows downhill.
• In a electrochemical or voltaic cell, the energy
  of the electrons is harnessed as they flow
  downhill in terms of energy.
• Electrochemical/voltaic cells are spontaneous.
  They are used to produce electricity.

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Parts of an electrochemical cell

• Cathode the electrode where reduction occurs
  (Cathode and reduction both begin with a
  consonant.)
• Anode the electrode where oxidation occurs
  (Anode and oxidation both begin with a vowel).
• Salt Bridge part of a voltaic cell that
  prevents positive
• or negative charge from building up at the
  electrodes. Ions
• flow through the salt bridge.

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How to keep them straight!
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The parts of a voltaic cell
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The parts identified
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Electrolytic Cells

• Redox reaction that uses electrical energy to
• produce chemical energy.
• (Ex. Electroplating, re-charging batteries)

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Pumping electrons uphill

• To continue the analogy to water, the
  electrolytic cell is like pumping water uphill,
  it requires energy.
• In an electrolytic cell the electrons are
  pumped uphill by a power source.
• Electrolytic cells are non-spontaneous. They
  require energy to take place.

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COMPARISON OF VOLTAIC AND ELECTROLYTIC CELLS
SPONTANEOUS
NON-SPONTANEOUS
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One use of electrolytic cells is electroplating
where electricity is used to deposit a thin layer
of metal atoms on the surface of an object.
Remember Electrolytic cells are non-spontaneous.
They require a power source to take place.
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Which way do the electrons flow?

• When two half cells are hooked together, how does
  one determine which one will be oxidized (give
  off electrons) and which one will be reduced
  (gain electrons)?
• The answer to that question can be provided by
  Table J
• The Activity Series

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Determining the direction the electrons flow in
Voltaic Cells
Electrons flow from the more active metal to the
less active metal
Electrons flow from the less active non-metal to
the more active non-metal
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A sample problem

• Suppose a Cu/Cu2 half cell and a Ag/Ag half
  cell are connected to form a battery. Which way
  will the electrons flow?
• Based on Table J, Cu is a more active metal than
  Ag. Therefore, the electrons will flow from the
  Cu/Cu2 half-cell to the Ag/Ag half-cell.

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You try one!

• Suppose a Fe/Fe3 half cell and a Al/Al3 half
  cell are connected to form a battery. Which way
  will the electrons flow?
• Did you say the electrons would flow from the Al
  to the Fe? Thats what Table J tells us!