1 / 16

Chapter 14 – Fundamentals of Electrochemistry

Chapter 14 – Fundamentals of Electrochemistry. Homework - Due Friday, April 1 Problems: 14-4, 14-5, 14-8, 14-12, 14-15, 14-17, 14-18, 14-25, 14-26, 14-41, . Electrochemistry Review of the Basics. Oxidation Loss of electrons Always occurs at the anode

jovianne
Download Presentation

Chapter 14 – Fundamentals of Electrochemistry

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. Chapter 14 – Fundamentals of Electrochemistry Homework - Due Friday, April 1 Problems: 14-4, 14-5, 14-8, 14-12, 14-15, 14-17, 14-18, 14-25, 14-26, 14-41, CHM 320 - Lecture 23 Chapt 14

  2. Electrochemistry Review of the Basics • Oxidation • Loss of electrons • Always occurs at the anode • Happens because of the action of a reducing agent • Reduction • Gain of electrons (charge is reduced) • Always occurs at the cathode • Happens because of the action of the oxidizing agent Fe+3 + e- = Fe+2 CHM 320 - Lecture 23 Chapt 14

  3. Redox Reaction ox1 + red2 = red1 + ox2 Example: 2(e- + Fe+3 = Fe+2) + Sn+2 = Sn+4 + 2 e- ------------------------------------------- 2 Fe+3 + Sn+2 = 2 Fe+2 + Sn+4 So… ox1= Fe+3 , red2 = Sn+2, red1=Fe+2, ox2=Sn+4 CHM 320 - Lecture 23 Chapt 14

  4. 4 Electric Charge (in Coulombs) and Work • Voltage represents electrical potential (potential to do work) • If some total charge in coulombs (q) is moved through some electrical potential (E, in volts V) then work is done! • The charge in coulombs (q) is equal to the number of moles of electrons (n) times the Faraday Constant (F) CHM 320 - Lecture 23 Chapt 14

  5. Ohm’s Law and Power • Ohm’s law relates electrical resistance, current and potential! • Power is the work done in some unit time (e.g. joules of work per second) • The units of Power are Watts (W) • Ohm’s law and power are related! CHM 320 - Lecture 23 Chapt 14

  6. Let’s Work Some Problems • A 6.00V battery is connected across a 2.00 K resistor, how many electrons flow through the circuit per second? • How many joules of heat (heat is work) are produced per electron? • What voltage would the battery need to be to deliver a power at 100.0 Watts? CHM 320 - Lecture 23 Chapt 14

  7. Electrochemical Cells • There are two basic electrochemical cells: • A GALVANIC cell uses spontaneous chemical reactions to generate electricity • A ELECTROYLTIC cell requires an electrical potential to be applied to the cell to drive some reaction. • A complete cell contains: • anode • cathode • completed circuit (for electrons to flow) • a salt bridge (usually!) • an electrolyte solution • chemical species that undergo reaction. CHM 320 - Lecture 23 Chapt 14

  8. Galvanic Cell Cells and Cell Reactions Overall Cell Reaction Zn(s) + Cu+2(aq) ---> Zn+2(aq) + Cu(s) oxidation half reaction anode Zn(s) ---> Zn+2(aq) + 2 e- reduction half reaction cathode Cu+2(aq) + 2 e- ---> Cu(s) CHM 320 - Lecture 23 Chapt 14

  9. CHM 320 - Lecture 23 Chapt 14

  10. CHM 320 - Lecture 23 Chapt 14

  11. What is happening at the electrode(s) and how do we describe the cell? CHM 320 - Lecture 23 Chapt 14

  12. The Standard Hydrogen Electrode (SHE) • The basis by which all other measurements are made. • Assigned a potential of zero by definition! • Not practical for regular use Hydrogen Half-Cell H2(g) = 2 H+(aq) + 2 e- reversible reaction SHE consists of a platinum electrode covered with a fine powder of platinum around which H2(g) is bubbled. Its potential is defined as zero volts. CHM 320 - Lecture 23 Chapt 14

  13. CHM 320 - Lecture 23 Chapt 14

  14. CHM 320 - Lecture 23 Chapt 14

  15. Standard Potentials • Standardized potentials (Eo), listed as reductions, for all half-reactions • Measured versus the S.H.E (0) • Used in predicting the action in either a galvanic cell or how much energy would be needed to force a specific reaction in a non-spontaneous cell • Assumes an activity of one for the species of interest (usually a fair approximation) at a known temperature in a cell with the S.H.E. • Assumes that the cell of interest is connected to the (+) terminal of the potentiometer (voltmeter) and the S.H.E. is connected to the (-) terminal CHM 320 - Lecture 23 Chapt 14

  16. Better Oxidizing Agents in upper left hand corner. Better Reducing Agents in lower Right hand corner CHM 320 - Lecture 23 Chapt 14

More Related