Chapter 6 LAB

• Electrochemistry


  The branch of chemistry that deals with the interconversion of electrical energy and chemical energy
• Electrochemical processes


  Redox reactions in which the energy released by spontaneous reaction is converted to electricity, or in which electrical energy is used to cause a nonspontaneous reaction to occur
• Oxidation number


  The charge of an atom (free state or in a molecule) if electrons around it were completely transferred, rather than shared
• Balancing redox reactions


  1. Split the equation into two half equations

  2. Balance the atoms other than O and H before balancing them sequentially (O first then H). When balancing O, add water (H2O). When balancing H, add H+

  3. Balance the charges by adding electrons to the side with the higher charge

  4. Combine the half equations, making sure that the number of electrons are equal

  5. If you want an equation in the basic media, add enough OH- in the final equation equal to the number of H+
• Reduction reaction


  Reactions where electrons are gained by the species
• Oxidation reaction


  Reactions where electrons are given off by the species
• Electrochemical cell


  A system consisting of electrodes that dip into an electrolyte and in which a chemical reaction either uses or generates an electric current
• Voltaic/Galvanic cell


  An electrochemical cell in which a spontaneous reaction generates an electric current
• Electrolytic cell


  An electrochemical cell in which an electric current drives an otherwise nonspontaneous reaction
• Anode


  The electrode at which oxidation occurs
• Cathode


  The electrode at which reduction occurs
• Salt bridge


  A tube on an electrolyte in a gel that is connected to the two half-cells of a voltaic cell; the salt bridge allows the flow of ions but prevents the mixing of the different solutions that would allow direct reaction of the cell reactants
• By convention, oxidation reactions are on the anode (left) and reduction reactions are on the cathode (right)
• Standard hydrogen electrode


  A reference electrode used to measure the standard reduction potential of other half-cells
• Standard potential


  The potential difference between a half-cell and the standard hydrogen electrode under standard conditions
• Equilibrium constant and free energy


  They are related through the equation: ΔG = -RT ln K
• Nernst equation


  Relates the reduction potential of a half-cell to the standard reduction potential, the concentrations of the reactants and products, and the temperature