Electrochemistry pt II

  1. Standard cell potential (Ecell°) is the cell potential measured when all species are in their ______ states. In practice, this condition means that all gases are at ___, all solutes are at ___ mol*L-1, and all liquids and solids are ____.
    • standard 
    • 1 bar
    • 1
    • pure
  2. 3 steps on writing a cell reaction corresponding to a cell diagram
    • write the equation for the electrode on the right of the cell diagram as a reduction half-reaction (rmbr: right for reduction)
    • write the equation for the electrode on the left of the cell diagram as an oxidation half-reaction
    • multiply one or both equations by a factor if necessary to equalize the number of electrons, and then add the two equations. 
    • If the cell potential is positive, then the reaction is spontaneous as written, if it negative, then the reverse reaction is spontaneous
  3. Which is the cathode under standard conditions and why? What is the overall standard potential?
    MnO4- + 8H+ + 5e- → Mn2+ + 4H2O E=+1.51 V

    Cr2O72- + 14H+ + 6e- → 2Cr3+ + 7H2O E=+1.33V
    • The 1st one is, because the half reaction with higher standard potential is the cathode in a cell reaction with a positive potential
    • E = E(reduction) - E(oxidation) = 1.51V - 1.33V = +0.18V
  4. If solving for reaction gibbs free energy for Cu & Zinc ions, and your potential difference is +1.04V, which equation is used? What is the value of n?
    • ΔG = -nFE
    • n = 2mol
Card Set
Electrochemistry pt II
examples 14.4,14.5 & 14.9