Tang 04 electrolysis 2

2,425 views

Published on

Published in: Technology, Business
0 Comments
3 Likes
Statistics
Notes
  • Be the first to comment

No Downloads
Views
Total views
2,425
On SlideShare
0
From Embeds
0
Number of Embeds
1,079
Actions
Shares
0
Downloads
0
Comments
0
Likes
3
Embeds 0
No embeds

No notes for slide

Tang 04 electrolysis 2

  1. 1. ELECTROLYSIS
  2. 2. <ul><li>electrolysis – a process in a cell where an external source of energy is required to drive a non-spontaneous reaction </li></ul><ul><li>Compared to a galvanic cell, electrons are flowing in the opposite direction. </li></ul><ul><li>A car battery is an electrochemical cell when discharging and an electrolytic cell when charging. </li></ul>ELECTROLYSIS
  3. 3. Electrolytic Cells <ul><li>Galvanic Cell Electrolytic Cell </li></ul><ul><li>oxidation at anode; reduction at cathode </li></ul><ul><li>anions move to anode; cations move to cathode </li></ul><ul><li>These statements are true as the label of anode and cathode are opposite in the two cell types. </li></ul>ELECTROLYSIS
  4. 4. Galvanic vs. Electrolytic Cells ELECTROLYSIS
  5. 5. Electrolytic Cells <ul><li>Galvanic Cell </li></ul><ul><li>spontaneous rxn </li></ul><ul><li>E° > 0 </li></ul><ul><li>exothermic rxn </li></ul><ul><li>energy produced </li></ul><ul><li>anode  -ve electrode </li></ul><ul><li>cathode  +ve electrode </li></ul><ul><li>Electrolytic Cell </li></ul><ul><li>non-spontaneous rxn </li></ul><ul><li>E° < 0 </li></ul><ul><li>endothermic rxn </li></ul><ul><li>energy added </li></ul><ul><li>anode  +ve electrode </li></ul><ul><li>cathode  -ve electrode </li></ul>ELECTROLYSIS
  6. 6. Electrolytic Cell ELECTROLYSIS
  7. 7. <ul><li>Example #1: Identify the half-reactions that occur in an electrolytic cell containing a solution of NaCl. </li></ul><ul><li>Calculate the E° value of the full cell reaction from the half-cell values. </li></ul>Power Supply - - - - + + + + - + Cathode (strongest oxidizing agent) anode (strongest reducing agent) Na + Cl - Direct current Reduction: Na + + e -  Na (s) E˚= -2.71V Oxidation: 2Cl -  Cl 2 + 2e - E˚= -1.36V 2 Na + + 2 e -  2 Na (s) E˚= -2.71V 2Cl -  Cl 2 + 2e - E˚= -1.36V 2Na + + 2Cl - 2Na (s) + Cl 2 E˚= -4.07V electrolysis ELECTROLYSIS
  8. 8. Electrolytic Cells <ul><li>Electrolysis is used in the process of electroplating . A thin coat of one metal is used to cover another type of metal. </li></ul><ul><li>chromium to cover steel to prevent rusting </li></ul><ul><li>gold or silver to cover jewelry made of less expensive metals </li></ul>ELECTROLYSIS
  9. 9. Electrolytic Cells ELECTROLYSIS

×