1 / 17

Voltaic Cells

Voltaic Cells. Harnessing the power of Redox. Get out your notes + Chem Data Booklet. Redox Basics. Redox Reactions happen when one substance loses electrons (oxidized) and one gains electrons (reduced) Electrons are flowing. 2 Electrons. 2Na. 2Na +. Cl 2. 2Cl -.

jason
Download Presentation

Voltaic Cells

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. VoltaicCells Harnessing the power of Redox Get out your notes + Chem Data Booklet

  2. Redox Basics • Redox Reactions happen when • one substance loses electrons (oxidized) and • one gains electrons (reduced) • Electrons are flowing 2 Electrons 2Na 2Na+ Cl2 2Cl- Half equation #1: 2Na  2Na+ + 2e- Half equation #2: Cl2 + 2e-  2Cl- nett: 2Na + Cl2 2Na + 2Cl-

  3. Example Reaction Zn + Cu2+ Cu + Zn2+ Gains 2 electrons- reduced Loses 2 electrons- oxidized Zn Cu Cu2+ Zn2+ Zn  Zn2+ = +0.76 Cu2+  Cu = +0.34 Overall = +1.10

  4. Harness Electrons • If the reactants are separated • The electrons cannot travel directly between reactants • Those electrons can be used to do work • Note: the electrons will always flow in the direction which gives a +Eocell • Eocell = Eo(red)-Eo(ox)

  5. Build a Cell 1 (Ch 20, sect 3) Electrode- carries electrons, may or may not be part of the reaction Reaction: Zn + Cu2+ Cu + Zn2+ Reaction: Zn + CuSO4 Cu + ZnSO4 Zn Cu SO42- Zn2+ Cu2+ SO42-

  6. Build a Cell 2 Electrons! Reaction: Zn + Cu2+ Cu + Zn2+ Zn Cu Zn2+ Cu2+

  7. Build a Cell 3 Electrons! Zn Zn Reaction: Zn + Cu2+ Cu + Zn2+ Cu Cu Zn2+ Cl- K+ Salt Bridge KCl Cu2+ Build up of - ions Build up of + ions

  8. Terminology • Electrode: conductor which allows electrons to enter or leave a cell (any conductive but unreactive material, sometimes part of the redox reaction) • Anode: oxidation electrode, negative (Zn) • Cathode: reduction electrode, positive (Cu) • Half-cell: half of the electrochemical cell where ox. or red. takes place. • Electrolyte: salt solution in a half-cell, always contains oxidized and reduced form

  9. Other Cells 1 Electrons! Reaction: Zn + 2H+ H2 + Zn2+ Zn H2 Pt Cl- Zn2+ Salt bridge H+ SO42-

  10. Other Cells 2 Electrons! Reaction: 2I- + 2Fe3+ I2 + 2Fe2+ Pt Pt Salt bridge I- Fe3+ e- e- Fe2+ I2

  11. Other Cells 3 Electrons! Reaction: Cl- + MnO4- Cl2 + Mn2+ 10Cl- + 2MnO4- + 16H+ 5Cl2 + 2Mn2++ 8H2O C Pt Salt bridge MnO4-/H+ Cl- e- e- Cl2 Mn2+

  12. Try it! • Draw a cell schematic to show the reaction: Cu  Cu2+ + 2e- I2 + 2e- 2I- (platinum electrode) Cu + I2 Cu2+ + 2I- • Label the anode, cathode, and direction of electron flow • Calculate the voltage

  13. Try It! Answer Electrons! • Cu + I2 Cu2+ + 2I- Cu Pt Anode- oxidation Cathode- reduction Salt bridge I2 Cu2+ Voltage = -0.34 + 0.54 = 0.20V

  14. Videos • Galvanic cells (2 min) • Animation (24 sec) • Li Batteries (5.5 min) • Potentials (2 min) • Song(3.5 min, This guy is seriously prolific)

More Related