electrochemistry ch 17 n.
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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

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moving electrons
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
  • 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


electrolytic cell
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

using electrolysis
Using Electrolysis
  • Removing elements from compounds:


  • 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
refining ores
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

refining aluminum
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


  • What is oxidized/reduced?

Al; +30, reduced C; 0+4; oxidized

  • 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
electrolytic cleaning
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
electrochemical cells
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
potential difference
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?


Not very reactive; wont corrode

galvanic cells
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

types of batteries
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-
types of batteries1
Types of Batteries
  • Lead Storage Battery
    • Lead (IV) Oxide electrode
    • Lead electrode
    • Sulfuric acid electrolyte
  • Lead (IV) is reduced and Lead is oxidized



  • Pb2+combines with SO42- ions
  • Both anode and cathode collect PbSO4
  • Reaction reversible
alternative batteries
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
alternative batteries1
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