Voltaic Cells

• Anode


  Negative electrode
• Cathode

  Positive electrode
• In spontaneous redox rxns, e- are transferred and energy is released
• Energy can be used to do

  work
• Voltaic Cell (battery)

  Spontaneous redox rxn
• A voltaic cell

  Converts chemical energy into electrical energy (flow of e- produces electricity)
• How does it work?


  e- flow spontaneously from the anode (more active metal) to the cathode (less active metal)
• An Ox --> Anode

  Negative electrode where oxidation (loss of e-) occurs
• Red Cat ---> Cathode


  Positive electrode where reduction (gain of e-) occurs
• Parts of a Voltaic Cell

  • 2 half cells (1 for oxidation & 1 for reduction half rxns)
  • Electrodes (site of oxid. & red.)
  • wire connects to electrodes - allows - to How)
  • Salt Bridge (allows ions to flow and prevents the building of charges (maintains electrical neutrality)
  • Voltmeter (measures electric current)
• How to Label it?

  1. Find which electrode is the anode & which is the cathode

  2. Find where oxid. & red. takes place

  3. Find the direction of e- flow
• use Table J to find flow of e
• More active metal is oxidized
• e- will flow from high to low
• As e- flow, electrodes...

  Cathode increases in mass
• As e- flow, electrodes...

  Anode deceases in mass.
• The Red Cat gets fat
• Cathode (Reduction) increases in mass
• Function of the salt bridge


  Allows for flow of ions to present a build up as charge at each electrode
• Positive ions flow to cathode
• Negative ions flow to anode
• When Salt bridge is removed

  Voltage will became zero b/c e- stop flowing
• To find an element with many charges, but is combined with a polyatomic ion, go to table E to find the charge of the polyatomic ion. Then use alegebra to solve from there
• if writing a half rxn for oxidation or reduction in a voltaic cell, you have to always start from the element's subscript being 0 and then put the e- where they belong in the rxn and the element from the voltaic cell diagram will be on the products side
• Anions move towards the anode
• cations move towards the cathode
• Salt bridge functions?


  Maintains electrical neutrality & allows flow of ions
• Redox reaction


  Electrons are transferred from the oxidizing elements which loses to the reducing element which gains
• LEO


  Lose e- oxidation
• GER


  Gain e- reduction
• Voltaic cell or battery

  1. Oxidation occurs at the anode, which is negative charged

  2. Reduction occurs at the cathode, which is positive charged

  3. Electrons flow from the anode to the cathode
• Salt bridge


  Permits the flow of ions in the voltaic cell in order to maintain the charges of the anode and cathode
• Both the anode and cathode are electrodes, so they produce electricity in a voltaic and electrolytic cell.
• if question is asking why the mass of a specific electrode decreases or increases as the cell operates, in terms of the ion and atoms, if it's oxidation, say the atoms are oxidized to ions and if it's reduction, say the atoms are reduced to ions.