1 / 17

Electrochemical Cells (Batteries)

Electrochemical Cells (Batteries). Chemical reaction produces electricity. Called “voltaic cells” Happens SPONTANEOUSLY. Moving Electrons = Electricity. Electrons from oxidized substance travel towards substance reduced. Traveling electrons move through “external circuit”

pascha
Download Presentation

Electrochemical Cells (Batteries)

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. Electrochemical Cells (Batteries) Chemical reaction produces electricity. Called “voltaic cells” Happens SPONTANEOUSLY.

  2. Moving Electrons = Electricity Electrons from oxidized substance travel towards substance reduced. Traveling electrons move through “external circuit” where they do work.

  3. Parts of a Simple Battery (Voltaic Cell) Made of Two “Half Cells” containing: 2 Metal Electrodes 2 Solutions of Ions External Wire Salt Bridge

  4. “Charge” flows in a “circuit” that is connected. External Wire: allows e- to flow between metal electrodes Salt Bridge: allows ions to flow between solutions

  5. What is Ox/Red? Start with Table J Electrons travel from more “Active” metal toward less active metal. Metal above = oxidized Ion on Metal below = reduced Ex: Ox: Zn Red: Cu+2

  6. Which way do electrons flow in the external wire? Electrons flow “Down Table J” From metal above to ion of metal below from Zn to Cu+2 e-

  7. Which electrode is negative or positive? Electrons flow from negative to positive electrode. Negative electrode: Zn Positive electrode: Cu e-

  8. Which electrode is the anode or cathode? Anode: metal electrode where oxidation occurs Ex: Zn Cathode: metal electrode where reduction occurs Ex: Cu

  9. Remember AN OX RED CAT Anode is where oxidation happens Cathode is where reduction happens

  10. What are the Half Reactions? Ox: Zn0 Zn+2 + 2e- Red: Cu+2 + 2e- Cu0 What is the Net Equation? Net: (add ½ reactions) Zn0 + Cu+2 Zn+2 + Cu0 Make sure final net equation is balanced for electrons and atoms! e-

  11. Which electrode gains/loses weight? Look at half reactions!! Which forms solid metal? Which forms dissolved ions? Ox: Zn0 Zn+2 + 2e- Red: Cu+2 + 2e- Cu0

  12. Which way do the ions in the salt bridge “migrate” or move? Remember: “The negative ions complete the circuit” (The ions actually end up moving towards the solution of opposite charge that forms.)

  13. Dead Battery Voltage = 0 Means the reaction in the battery has reached EQUILIBRIUM.

  14. You try it… Mg/Mg+2//Al+3/Al • Draw and label Battery • What is oxidized/reduced? • What are the half reactions and net(balanced)? • What is the neg/pos electrode? • What is the anode/cathode? • Which way do e- flow in wire? • Which way do -/+ ions flow in salt bridge? • Which electrode gains/loses mass?

  15. Lemon Battery Demo • http://youtu.be/AY9qcDCFeVI • Batteries • http://www.mhhe.com/physsci/chemistry/essentialchemistry/flash/galvan5.swf • Battery Simulation http://www.chem.iastate.edu/group/Greenbowe/sections/projectfolder/flashfiles/electroChem/volticCell.htmlN • Nerst Equation Simulation (HONORS) http://www.chem.iastate.edu/group/Greenbowe/sections/projectfolder/flashfiles/electroChem/voltaicCellEMF.html

  16. Finding Voltage of a Battery (Honors) Use Voltage Table Find your half reactions and record voltage Note: All ½ reactions shown are reductions. For oxidation, reverse the sign of the voltage

  17. Nerntz Equation (Honors) Find voltage of a battery when the conc. of dissolved ions is not 1 Molar (as on “standard voltage” table) Ecell = E0 – 0.0592 log [product ion]x n [reactant ion]y n = total # of moles electrons being transferred The concentration of dissolved ions can affect voltage. Greater concentration of reactant ions (see net) increases the overall voltage.

More Related