Cell Potentials

• A galvanic cell has two electrodes which serves as the path through which electrons travel. Each electrode is immersed into an electrolyte involved in the reaction
• when an electrode experiences a greater electron "pressure" than another, this greater potential energy is known as electric potential
• If we allow the wire to pass through a voltmeter, we can measure the potential difference, E^o cell of the galvanic cell
• The salt bridge is a tube containing an electrolyte solution such as NaNO3 or KCl. The salt bridge neutralizes electrical charges in each halfcell by allowing the free flow of ions from one half-cell to another. Without the salt bridge, positive and negative charges will accumulate around the electrodes which will cause the reaction to stop
• The cell notation is a shorthand way to describe the overall reaction in a galvanic cell. It excludes spectator ions or those ions that are not participating in the reaction
• The reference cell that we use is the standard hydrogen electrode, SHE
• The standard hydrogen electrode has its standard electrode potential defined as zero (Eo reference = 0.0V)
• The SHE is the reference electrode used to measure the standard reduction potentials of other half-cells
• The standard reduction potential, Eo half-cell, is the potential of a given half-reaction when all the components are in their standard states which is described as 25oC, pressure of 100 kPa, 1 M concentration for aqueous solutions
• The half-cell potentials are not absolute quantities but are values relative to the reference standard
• The bigger the value of Eo , the more readily the reaction (as written) occurs
• We can see from the balanced chemical equation that as the galvanic cell operates, the mass of the anode decreases while the mass of the cathode increases
• T or F: Oxidation occurs in the anode.

  True
• T or F: The anode carries a negative charge.

  True
• T or F: The oxidation number of chemical species decrease at the cathode

  True
• T or F: The standard reduction potentials are measured at room temperature

  True
• T or F: Electrons flow from the anode to the cathode through the salt bridge.

  False
• T or F: The electrode potentials are measured relative to the standard hydrogen electrode.

  True
• T or F: Eo cell are written as reduction half-reactions

  True
• T or F: The anode has the more positive the Eo half-cell.

  False
• T or F: For the oxidation half-reaction, the value of the Eo half-cell is reversed.

  True
• T or F: The more positive the Eo cell, the stronger the oxidizing agent.

  True