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Uses of Standard Reduction Potentials. 2. Determine if oxidizing and reducing agent react spontaneously. . Cathode. Ered (cathode). . . Anode. Ecell (V). Ered (anode). Ecell > 0 : spontaneousEcell < 0 : nonspontaneous. Uses of Standard Reduction Potentials. 3. Calculate EcellEcell = Ecat
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1. Uses of Standard Reduction Potentials 1. Compare strengths of reducing/oxidizing agents.
the more - E°, stronger the red. agent
the more + E°, stronger the ox. agent
2. Uses of Standard Reduction Potentials 2. Determine if oxidizing and reducing agent react spontaneously
3. Uses of Standard Reduction Potentials 3. Calculate E°cell
E°cell = E°cathode - E°anode
Greater E°cell, greater the driving force!
4. Cell Potential Is there a relationship between Ecell and DG for a redox reaction?
Under standard state conditions: DG° = -nFE°cell
5. Equilibrium Constants from Ecell Under standard state conditions:
DG° = -nFE°cell
DG° = -RTlnK (from chapter 20)
-nFE°cell = -RTlnK
E°cell = (-RT/nF) lnK
8. More Problem Solving Calculate E°cell, DG°, and K for the voltaic cell that uses the reaction between Ag and Cl2 under standard state conditions at 25°C.
11. Problem Solving Calculate the voltage produced by the voltaic cell using the reaction between Zn(s) and Cu2+(aq) if [Zn2+] = 0.001 M and [Cu2+] = 1.3 M.
Zn(s) + Cu2+(aq) ? Zn2+(aq) + Cu(s)
15. Figure: 18-14
Title:
Corrosion prevention
Caption:
Figure 18.14 A layer of zinc protects iron from oxidation, even when the zinc layer becomes scratched. The zinc (anode), iron (cathode), and water droplet (electrolyte) constitute a tiny galvanic cell. Oxygen is reduced at the cathode, and zinc is oxidized at the anode, thus protecting the iron from oxidation.
Figure: 18-14
Title:
Corrosion prevention
Caption:
Figure 18.14 A layer of zinc protects iron from oxidation, even when the zinc layer becomes scratched. The zinc (anode), iron (cathode), and water droplet (electrolyte) constitute a tiny galvanic cell. Oxygen is reduced at the cathode, and zinc is oxidized at the anode, thus protecting the iron from oxidation.
20. Figure: 18-19
Title:
Electrorefining of copper
Caption:
Figure 18.19 Electrorefining of copper metal. (a) Alternating slabs of impure copper and pure copper serve as the electrodes in electrolytic cells for the refining of copper. (b) Copper is transferred through the CuSO4 solution from the impure Cu anode to the pure Cu cathode. More easily oxidized impurities (Zn, Fe) remain in solution as cations, but noble metal impurities (Ag, Au, Pt) are not oxidized and collect as anode mud.
Figure: 18-19
Title:
Electrorefining of copper
Caption:
Figure 18.19 Electrorefining of copper metal. (a) Alternating slabs of impure copper and pure copper serve as the electrodes in electrolytic cells for the refining of copper. (b) Copper is transferred through the CuSO4 solution from the impure Cu anode to the pure Cu cathode. More easily oxidized impurities (Zn, Fe) remain in solution as cations, but noble metal impurities (Ag, Au, Pt) are not oxidized and collect as anode mud.
23. Quantifying Aspects of Electrolysis How many kg of Al can be produced in 8.00 h by passing a constant current of 1.00 x 105 A through a molten mixture of Al oxide and cryolite?
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