1 / 19

Electrochemistry

Electrochemistry. Electrochemical Cells/ Chemical Cells. Also called voltaic or galvanic cells A redox reaction produces electricity Occurs spontaneously. Electrochemical Cell. Half Cells. Each ½ of the redox reaction occurs in a separate container One for oxidation and one for reduction

torrance-prior
Télécharger la présentation

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. Electrochemistry

  2. Electrochemical Cells/Chemical Cells • Also called voltaic or galvanic cells • A redox reaction produces electricity • Occurs spontaneously

  3. Electrochemical Cell

  4. Half Cells • Each ½ of the redox reaction occurs in a separate container • One for oxidation and one for reduction • They are connected by a salt bridge • Salt Bridge: allows ions to flow between the two cells

  5. Electrodes • Metals which provide a surface for oxidation or reduction to occur • Solids • Oxidation Number = 0 • Anode • Cathode

  6. ANODE • Oxidation occurs at the anode • Negative electrode • CATHODE • Reduction occurs at the cathode • Positive electrode Red Cat – An Ox Reduction at the Cathode Oxidation at the Anode

  7. Flow of Electrons • The electrodes are connected by a wire • Electrons flow from the anode to the cathode through the wire

  8. Why does the cell produce electricity? • There is a difference of electric potential between the two electrodes • Electrons will flow between the two electrodes until equilibrium is reached • At equilibrium the cell’s voltage would be zero

  9. Zn Zn2+ + 2e- Electrons needed here for reduction Electrons released here by oxidation Zn + CuSO4 Cu + ZnSO4 Red Cat -reduction takes place…electrons are gained. An Ox -oxidation takes place…electrons are lost. Cu2+ + 2e - Cu0 e- e- e- e- e- - e- + e- e- e- e- e-

  10. Batteries • Use a redox reaction which produces electricity spontaneously • Batteries are recharged by reversing the reaction • Dry Cell (Acid or Alkaline), Lead Storage (Car), Rechargeable (Ni/Cd)

  11. Corrosion • Oxidation of a metal • Metal combines with element (usually oxygen) Example: 4Fe + O2 2Fe2O3 (rust)

  12. Prevention of Rust • Cover the metal – paint, oil, another (more reactive) metal • Cathodic Prevention • metal is placed in contact with a more reactive metal • That metal will be oxidized (acts as the anode), the original metal acts as the cathode • Alloys – mixture of metals • Brass, stainless steel (Fe + Cr), cast iron (C + Si)

  13. Electrolytic Cells • Also called electrolysis • An electric current is used to produce a chemical reaction • An electric current is used to force a non-spontaneous reaction to occur

  14. Oxidation occurs at the anode • Reduction occurs at the cathode • Electrons flow from anode to cathode • The cathode is the negative electrode • The anode is the positive electrode • This is opposite of the chemical cell because the external current causes the polarities to switch

  15. Electroplating • Object to be plated is the CATHODE, negative • Metal to be plated onto the object is the ANODE, positive • Solution must contain ions of the metal to be plated

  16. Silver Plating • Cathode = • Anode = • Solution = • What happens to the mass of each electrode during the reaction?

  17. Electrolysis of Water 2 H2O  2 H2 + O2 • The H+ is reduced at the (-) cathode, producing H2 (g), which is trapped in the tube • The O2 is oxidized at the (+) anode, yielding O2 (g), which is trapped in the tube

  18. Hydrogen Fuel Cells • Uses hydrogen gas as the fuel 2 H2 + O2  2 H2O

More Related