AP Chemistry Unit 9.9 Cell Potential Under Nonstandard Conditions

Cell Potential Under Nonstandard Conditions

  • As the cell runs, the redox reaction is getting back to equilibrium
  • Any Ecell value anything other than 0 is running and producing voltage → A running galvanic cell is NOT at equilibrium!
  • A dead battery is a galvanic cell that has reached equilibrium (Ecell = 0V and Q = K) → the 2 cell components have the same free energy

The Nernst Equation

  • Will be asked to predict whether the cell potential is going to be less than, equal to, or greater than what it normally would be under standard conditions

Cell Potential and Concentration

  • Using the reaction quotient, Q, we can predict the change in Ecell
  • Q > 1 → Ecell < E°cell (voltage decreases)
  • Q < 1 → Ecell > E°cell (voltage increases)
  • The ability of a nonstandard & standard cell to power a device depends on the concentration of ions
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