Electrochemistry I: Chemical Cells

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Electrochemistry I Chemical Cells

• Experiment 32

2
Electrochemistry

• Electrochemistry is the study of electron
  transfer or oxidation-reduction reactions.
• LEO goes GER!!!!
• Oxidation is a loss of electrons.
• Reduction is a gain of electrons.
• In voltaic cells, also called galvanic cells, a
  spontaneous chemical reaction occurs, generating
  an electric current.

3
Review Oxidation Reduction

• Consider the following reaction
• Mg(s) Cu2(aq) ? Mg 2(aq) Cu(s)
• Where is oxidation taking place? Where is
  reduction taking place?
• Write half-reactions

4
Review Oxidation Reduction

• Consider the following reaction
• Mg(s) Cu2(aq) ? Mg 2(aq) Cu(s)
• Where is oxidation taking place? Where is
  reduction taking place?
• Write half-reactions
• Mg(s) ? Mg 2(aq) 2e - (LE Oxidation)
• Cu2(aq) 2e- ? Cu(s) (GE Reduction)

5
Question????

• In your reaction, metallic magnesium has replaced
  the copper (II) ion in the solution.
• Why is this possible?
• Will metallic copper replace magnesium ion in
  solution?

6
The Electromotive or Reactivity Series

• Review from 1411
• The reactivity series puts the metallic elements
  in order of their relative reactivity.
• An element can replace any element below it.

7
Voltaic Cells

• In the reactions I showed you, the magnesium and
  zinc come into direct contact with the copper
  ions. This allows the electrons to flow directly
  from the metal to the ions.
• By physically separating the metal from the ions
  and connecting them by a wire, you create a
  voltaic cell, or battery.

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More Voltaic Cells

• The following link leads you to the homepage for
  chapter 18 of your textbook.
• Click on Activities
• Then click on the movie about galvanic cells.
• http//wps.prenhall.com/esm_mcmurry_chemistry_4/0,
  7623,620625-,00.html

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Procedure Notes

• All salts may go down the drain with plenty of
  water.
• Follow the directions in your lab manual!!!