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Topic: Redox

Topic: Redox. Aim: What are electrochemical cells? Do Now: Which of the following ions is most easily reduced? Li+ 2) K+ 3) Ca 2+ 4) Na+ HW:. Types of Cells. Electrochemical Cells. Practical uses for redox reactions Involve: Chemical rxns Flow of e- 2 types:

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Topic: Redox

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  1. Topic: Redox Aim: What are electrochemical cells? Do Now: Which of the following ions is most easily reduced? Li+ 2) K+ 3) Ca2+ 4) Na+ HW:

  2. Types of Cells

  3. Electrochemical Cells • Practical uses for redox reactions • Involve: • Chemical rxns • Flow of e- • 2 types: • Voltaic (galvanic) • Electrolytic

  4. Voltaic Cell • produce electricity as a result of chemical rxns • These rxns are spontaneous • These rxns cause the flow of e-. Therefore, electricity is produced. • Parts of a voltaic cell (drawn on board)

  5. Voltaic Cell

  6. Parts of Voltaic Cell 1. Two Half Cells: - Each half of the redox reaction takes place in a separate container. - The 2 containers (2 half cells) are connected by a SALT BRIDGE. - Allows ions to move, but does not allow the solutions to mix! 2. Electrodes a. Anode – where oxidation occurs (LEO) An Ox b. Cathode – where reduction occurs (GER) Red Cat

  7. Parts, cont. 3. Salt Bridge 4. Switch 5. Wire 6. Voltmeter 7. Solutions in Both Half Cells

  8. Voltaic Cell Info • ANODE is NEGATIVE • CATHODE is POSITIVE • (Think: they are in alphabetical order!) • Electrons flow from anode to cathode b/c opposites attract (e- are negative, cathode is positive) • Also, anode is oxidation – loss of e-, cathode is reduction – gain of e- • This spontaneous flow produces electricity.

  9. Voltaic Cell Info • When given a voltaic cell, how do you know which metal electrode is the anode and which is the cathode? • The metal HIGHER ON TABLE J will be the ANODE and LOSE ELECTRONS b/c it is MORE EASILY OXIDIZED than the other metal (below it)!

  10. Review Questions • In the reaction:Zn  Zn2+ + 2e-Is Zn oxidized or reduced? • In the reaction:Zn + Cu2+ Zn2+ + CuWhich is reduced, Cu2+, Cu, Zn2+, or Zn? • Which one has a stronger tendency to lose electrons when they are in contact with an electrolyte, Cu2+, Cu, Zn2+, or Zn?

  11. Review Questions • What is responsible for the conduction of electricity in the solution? • The salt-bridge is the path for what to move?

  12. Examples of Voltaic Cells • Batteries • a dry cell battery is what you find in your typical electronic device. • The reason you often need more than one battery is because a single battery doesn’t provide enough volts of power. When connected in a series (end to end), the voltage is multiplied.

  13. Electrolytic Cells • produce chemical reactions as a result of electric current • These rxns are non-spontaneous • These rxns use the flow of e-. Therefore, electricity is used. • Parts of an electrolytic cell (drawn on board)

  14. Electrolytic Cell

  15. Parts of Electrolytic Cell 1. One Cell: - Both halves of the redox reaction take place in the same container. 2. Electrodes a. Anode – where oxidation occurs (LEO) An Ox b. Cathode – where reduction occurs (GER) Red Cat

  16. Parts, cont. • Wire • Battery/power source • Solution in Cell

  17. Electrolytic Cell Info • ANODE is POSITIVE • CATHODE is NEGATIVE • Electrons still flow from anode to cathode b/c opposites attract (e- are negative, cathode is positive) • Also, anode is oxidation – loss of e-, cathode is reduction – gain of e-

  18. Electroplating

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