1 / 16

Electrochemistry Ch. 17

Electrochemistry Ch. 17. Moving Electrons. What kind of chemical reaction relates to the concept of electricity? Redox Reactions: electrons are moving from atom to another; moving electrons produce electricity Battery : controlled chemical reaction to produce an electrical current

jed
Télécharger la présentation

Electrochemistry Ch. 17

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. ElectrochemistryCh. 17

  2. Moving Electrons • What kind of chemical reaction relates to the concept of electricity? Redox Reactions: electrons are moving from atom to another; moving electrons produce electricity • Battery: controlled chemical reaction to produce an electrical current • Electrolysis: using electricity to causes a chemical reaction

  3. Electrolysis • Electrolytic cell- device, when attached to a power source (battery) induces a chemical reaction • Two Electrodes: Cathode- releases electrons, takes in Cations (negatively charged) Anode- takes electrons, takes in Anions (positively charged) • REDCAT??? REDuction at the CAThode Oxidation at the Anode ????

  4. Electrolytic Cell • If the following compound was separated using electrolysis: 2Al2O3  4Al(s) + 3O2(g) • What is oxidized/reduced? • What are the cations/anions? • What elements will move to the cathode/anode? Al; +30, reduced O; -20, oxidized Al+3Cation O-2Anion Al+3Cathode O-2Anode

  5. Using Electrolysis • Removing elements from compounds: 2NaCl(aq)+2H2O(l)Cl2(g)+H2(g)+2NaOH(aq) • Refining Ores- remove pure metal from compounds found in the Earth • Electroplating- cheap and effective why to coat and protect reactive metals • Electrolytic Cleaning- restoring aged materials

  6. Refining Ores • Before refining aluminum was possible, pure aluminum was more rare than gold or sliver • Today it is one of the most widely used metals Bauxite Ore Pure Aluminum • Heat the Bauxite Ore to remove water and impurities. What is a compound with H2O inside it? A Hydrate 2) Al2O3 is heated to about 1000oC 3) Molten Al2O3 goes through electrolysis

  7. Refining Aluminum • In a electrolytic cell with Carbon anodes, oxygen is drawing towards the carbon to produce CO2 • Al ions settle on the bottom of the container making pure liquid aluminum 2Al2O3(s)+3C(s)4Al(l)+3CO2(g) • What is oxidized/reduced? Al; +30, reduced C; 0+4; oxidized

  8. Electroplating • Reactive metals need a protective coating to prevent rusting or tarnishing • Zinc makes a great coat for steel • Metal plating using gold, silver, and copper is also common • Object to be plated cathode • Metal coating anode

  9. Electrolytic Cleaning • Cleaning objects by pulling ions of chemical build up • Antiques coated in salts • Old object cathode • Stainless steel anode • Chlorine and other salt compounds can be removed

  10. Electrochemical Cells • A spontaneous redox reaction that can be used to produce an electrical current • Required: • A metal cathode; site of reduction • A metal anode; site of oxidation • An electrolyte solution; allow transfer of electrons • The type of metal used determines if it is a cathode or an anode • Metal more easily reduced is cathode • Metal more easily oxidized is anode

  11. Potential Difference • The type of metal and the amount used determines the strength of the electrical current • Potential difference- difference between how easily the anode is oxidized and the cathode is reduced • Voltage (Alessandro Volta) • Which produces a larger voltage; a current between Lithium/Zinc or Sodium/Magnesium? • Why is it better to make jewelry out of Gold, Silver, Copper, and Platinum? Lithum/Zinc Not very reactive; wont corrode

  12. Galvanic Cells • Battery (voltaic cell)- controlled spontaneous redox reaction to produce a current • Mg/Cu Galvanic Cell: • What is oxidized/reduced? What is the cathode/anode? • MgSO4 and CuSO4 containers are connected by a salt bridge • Keeps solutions separate but allows ion movement • Mg2+ ions build up at anode; Cu2+ removed at cathode • Salt ions neutralize a build up of charges as the Mg2+/Cu2+ change places Mg: oxidized; becomes the anode Cu: reduced; becomes the cathode

  13. Types of Batteries • Carbon-Zinc Dry Cell • Carbon center (cathode); MnO2 coating • Zinc cover (anode) • Electrolyte gel (NH4Cl-ZnCl2) • Zinc is oxidized; Zn Zn2++2e- • Manganese is reduced; 2MnO2+H2O+2e- Mn2O3+2OH-

  14. Types of Batteries • Lead Storage Battery • Lead (IV) Oxide electrode • Lead electrode • Sulfuric acid electrolyte • Lead (IV) is reduced and Lead is oxidized Pb(metal)Pb2++2e- Pb+4+2e-Pb2+ • Pb2+combines with SO42- ions • Both anode and cathode collect PbSO4 • Reaction reversible

  15. Alternative Batteries • NiMH battery (Nickel + Metal Hydride) • Rechargeable • Use electrolysis to reverse the redox reaction • Lose 1% of their charge a day when even not used • Lithium battery • Holds a more charge • Li is easiest to oxidize (produces a large potential difference) • Li explodes in water

  16. Alternative Batteries • Hydrogen-Oxygen Fuel Cell • Electrodes are inert metals • Produces H2O as by-product • Could be possible alternative to gasoline cars • Hydrogen and Oxygen are very abundant elements on earth • Super Battery? • In 2009 a Lithium super battery was produced using nano-engineering • Releases energy 100 times faster • Could recharge an electric car faster than it takes to pump gas into a gasoline car

More Related