1. Notes on Electrolytic Cells
An electrolytic cell is a system of two inert (nonreactive) electrodes (C or Pt) and an electrolyte connected to a power supply. It has the following characteristics
     
1. Nonspontaneous redox reaction
2. Produces chemicals from electricity
3. Forces electrolysis to occur

2. When analyzing an electrolytic cell, your first and most important step is to determine the oxidation and reduction reactions.
Electrolytic Cell Main Rule
The electrode that is connected to the -ve terminal of the power supply will gain electrons and therefore be the site of reduction.

3. Other Rules: For Electrochemical and Electrolytic Cells
Oxidation always occurs at the anode and reduction at the cathode
Electrons flow through the wire and go from anode to cathode
Anions (- ions) migrate to the anode and cations (+ions) migrate towards the cathode.

4. 1. Draw and completely analyze a molten NaBr electrolytic cell.

5. 1. Draw and completely analyze a molten NaBr electrolytic cell.
Draw a beaker, two inert electrodes wired to a power supply.

6. 1. Draw and completely analyze a molten NaBr electrolytic cell.
Power Supply DC
Draw a beaker, two inert electrodes wired to a power supply.

7. 1. Draw and completely analyze a molten NaBr electrolytic cell.
Power Supply DC
Label the electrode with Pt or C.

8. 1. Draw and completely analyze a molten NaBr electrolytic cell.
Power Supply DC
Label the electrode with Pt or C. Pt

9. 1. Draw and completely analyze a molten NaBr electrolytic cell.
Power Supply DC
Add the electrolyte Pt Pt

10. 1. Draw and completely analyze a molten NaBr electrolytic cell.
Power Supply DC
Add the electrolyte
Molten or liquid means no water! Pt Pt
Na+
Br-

11. 1. Draw and completely analyze a molten NaBr electrolytic cell.
Power Supply DC
Label the negative and positive electrodes Pt Pt
Na+
Br-

12. 1. Draw and completely analyze a molten NaBr electrolytic cell.
Power Supply DC
Label the negative and positive electrodes Pt Pt _ +
Na+
Br-

13. 1. Draw and completely analyze a molten NaBr electrolytic cell.
Power Source
The negative is reduction and the positive is oxidation. Pt Pt _ +
Na+
Br-

14. 1. Draw and completely analyze a molten NaBr electrolytic cell.
Power Source
The negative is reduction and the positive is oxidation. Pt Pt +
oxidation _
reduction
Na+
Br-

15. 1. Draw and completely analyze a molten NaBr electrolytic cell.
Power Source
The anode is oxidation and the cathode is reduction. Pt Pt +
oxidation
anode _
reduction
cathode
Na+
Br-

16. 1. Draw and completely analyze a molten NaBr electrolytic cell.
The anion migrates to the anode and the cation to the cathode.
Power Source Pt Pt +
oxidation
anode _
reduction
cathode
Na+
Br-

17. 1. Draw and completely analyze a molten NaBr electrolytic cell.
Power Source
The anode reaction is the oxidation of the anion. Pt Pt +
oxidation
anode _
reduction
cathode
Na+
Br-

18. 1. Draw and completely analyze a molten NaBr electrolytic cell.
Power Source
The anode reaction is the oxidation of the anion. Pt Pt +
oxidation
anode
2Br- → Br2(g)+ 2e- _
reduction
cathode
Na+
Br-

19. 1. Draw and completely analyze a molten NaBr electrolytic cell.
Power Source
The Cathode reaction is the reduction of the cation. Pt Pt +
oxidation
anode
2Br- → Br2(g)+ 2e- _
reduction
cathode
Na+
Br-

20. 1. Draw and completely analyze a molten NaBr electrolytic cell.
Power Source
The Cathode reaction is the reduction of the cation. Pt Pt _
reduction
cathode
2Na+ + 2e- → 2Na(l) +
oxidation
anode
2Br- → Br2(g)+ 2e-
Na+
Br-

21. 1. Draw and completely analyze a molten NaBr electrolytic cell.
Power Source
Gas Br2 is produced at the anode. Pt Pt _
reduction
cathode
2Na+ + 2e- → 2Na(l) +
oxidation
anode
2Br- → Br2(g)+ 2e-
Na+
Br-

22. 1. Draw and completely analyze a molten NaBr electrolytic cell.
Power Source
Liquid Na is produced at the cathode. Pt Pt _
reduction
cathode
2Na+ + 2e- → 2Na(l) +
oxidation
anode
2Br- → Br2(g)+ 2e-
Na+
Br-

23. 1. Draw and completely analyze a molten NaBr electrolytic cell.
The potential for each half reaction is calculated and the oxidation sign is reversed
Power Source Pt Pt _
reduction
cathode
2Na+ + 2e- → 2Na(l) +
oxidation
anode
2Br- → Br2(g)+ 2e-
Na+
Br-

24. 1. Draw and completely analyze a molten NaBr electrolytic cell.
The potential for each half reaction is listed and the oxidation sign is reversed
Power Source Pt Pt _
reduction
cathode
2Na+ + 2e- → 2Na(l)
-2.71 v +
oxidation
anode
2Br- → Br2(g)+ 2e-
-1.09 v
Na+
Br-

25. 1. Draw and completely analyze a molten NaBr electrolytic cell.
The overall redox reaction is written.
Power Source Pt Pt _
reduction
cathode
2Na+ + 2e- → 2Na(l)
-2.71 v +
oxidation
anode
2Br- → Br2(g)+ 2e-
-1.09 v
Na+
Br-

26. 1. Draw and completely analyze a molten NaBr electrolytic cell.
The overall redox reaction is written.
Power Source Pt Pt _
reduction
cathode
2Na+ + 2e- → 2Na(l)
-2.71 v +
oxidation
anode
2Br- → Br2(g)+ 2e-
-1.09 v
Na+
Br-
2Na+ + 2Br- → Br2(g)+ 2Na(l) E0 = v

27. 1. Draw and completely analyze a molten NaBr electrolytic cell.
The minimum theoretical voltage MTV required to force this nonspontaneous reaction to occur is the negative of the cell potential.
Power Source Pt Pt _
reduction
cathode
2Na+ + 2e- → 2Na(l)
-2.71 v +
oxidation
anode
2Br- → Br2(g)+ 2e-
-1.09 v
Na+
Br-
2Na+ + 2Br- → Br2(g)+ 2Na(s) E0 = v

28. 1. Draw and completely analyze a molten NaBr electrolytic cell.
The minimum theoretical voltage MTV required to force this nonspontaneous reaction to occur is the negative of the cell potential.
Power Source Pt Pt _
reduction
cathode
2Na+ + 2e- → 2Na(l)
-2.71 v +
oxidation
anode
2Br- → Br2(g)+ 2e-
-1.09 v
Na+
Br-
2Na+ + 2Br- → Br2(g)+ 2Na(s) E0 = v MTV = v

29. 1. Draw and completely analyze a molten NaBr electrolytic cell.
Electrons flow through the wire from anode to cathode.
Power Source Pt Pt _
reduction
cathode
2Na+ + 2e- → 2Na(l)
-2.71 v +
oxidation
anode
2Br- → Br2(g)+ 2e-
-1.09 v
Na+
Br-
2Na+ + 2Br- → Br2(g)+ 2Na(s) E0 = v MTV = v

30. 1. Draw and completely analyze a molten NaBr electrolytic cell.
Electrons flow through the wire from anode to cathode.
Power Source e- e- Pt Pt _
reduction
cathode
2Na+ + 2e- → 2Na(l)
-2.71 v +
oxidation
anode
2Br- → Br2(g)+ 2e-
-1.09 v
Na+
Br-
2Na+ + 2Br- → Br2(g)+ 2Na(s) E0 = v MTV = v

31. 2. Draw and completely analyze a 1.0 M KI electrolytic cell.

32. 2. Draw and completely analyze a 1.0 M KI electrolytic cell.
Power Source Pt

33. 2. Draw and completely analyze a 1.0 M KI electrolytic cell.
Add the ions. (aq) or M
or solution means water.
Power Source Pt K+ I-
H2O

34. 2. Draw and completely analyze a 1.0 M KI electrolytic cell.
Label the -, +, anode, cathode, oxidation, and reduction.
Power Source Pt K+ I-
H2O

35. 2. Draw and completely analyze a 1.0 M KI electrolytic cell.
Label the -, +, anode, cathode, oxidation, and reduction.
Power Source Pt -
Cathode
reduction +
Anode
oxidation K+ I-
H2O

36. 2. Draw and completely analyze a 1.0 M KI electrolytic cell.
The cation and water migrate to the cathode
Power Source Pt -
Cathode
reduction +
Anode
oxidation K+ I-
H2O

37. 2. Draw and completely analyze a 1.0 M KI electrolytic cell.
The cation and water migrate to the cathode
Power Source Pt -
Cathode
reduction +
Anode
oxidation K+ I-
H2O

38. 2. Draw and completely analyze a 1.0 M KI electrolytic cell.
The cation or water reduces. The higher one on the chart is most spontaneous and occurs.
Power Source Pt -
Cathode
reduction +
Anode
oxidation K+ I-
H2O

39. Cl e- → 2Cl v
1/2O H+(10-7M) e- → H v
2H2O + 2e- → 2H OH v
Zn e- → Zn(s) v
K e- → K(s) v

40. Cl e- → 2Cl v
1/2O H+(10-7M) → H v
Reduction of water
2H2O + 2e- → 2H OH v
Zn e- → Zn(s) v
K e- → K(s) v

41. Cl e- → 2Cl v
1/2O H+(10-7M) → H v
Oxidation of water
Reduction of water
2H2O + 2e- → 2H OH v
Zn e- → Zn(s) v
K e- → K(s) v

42. Cl e- → 2Cl v
1/2O H+(10-7M) → H v
Oxidation of water
Reduction of water
2H2O + 2e- → 2H OH v
Zn e- → Zn(s) v
Reduction of K+
K e- → K(s) v

43. strongest oxidizing agent or highest
Cl e- → 2Cl v
1/2O H+(10-7M) → H v
Oxidation of water
strongest oxidizing agent or highest
Reduction of water select most spontaneous reaction
2H2O + 2e- → 2H2(g) OH v
Zn e- → Zn(s) v
Reduction of K
K e- → K(s) v
Overpotential Effect- treat water as if it were just below Zn

44. The overpotential effect is a higher than normal voltage required for the half reaction. This is often due to extra voltage required to produce a gas bubble in solution.

45. 2. Draw and completely analyze a 1.0 M KI electrolytic cell.
The cation or water reduces. The higher one on the chart is most spontaneous and occurs.
Power Source Pt -
Cathode
Reduction +
Anode
oxidation K+ I-
H2O

46. 2. Draw and completely analyze a 1.0 M KI electrolytic cell.
The cation or water reduces. The higher one on the chart is most spontaneous and occurs.
Power Source Pt -
Cathode
Reduction
2H2O+2e- → 2H2+ 2OH v +
Anode
oxidation K+ I-
H2O

47. 2. Draw and completely analyze a 1.0 M KI electrolytic cell.
The anion + water goes to the anode.
Power Source Pt -
Cathode
Reduction
2H2O+2e- → 2H2+ 2OH v +
Anode
oxidation K+ I-
H2O

48. 2. Draw and completely analyze a 1.0 M KI electrolytic cell.
For oxidation the most spontaneous reaction is found on the redox chart and is lowest.
Power Source Pt -
Cathode
Reduction
2H2O+2e- → 2H2+ 2OH v +
Anode
oxidation K+ I-
H2O

49. Cl e- → 2Cl v
1/2O2 + 2H+(10-7M) + 2e- → H v
Oxidation of water
I2(s) e- → 2I v
Reduction of water
2H2O + 2e- → 2H OH v
Zn e- → Zn(s) v
K e- → K(s) v

50. Cl e- → 2Cl v
1/2O2(g) + 2H+(10-7M) → H v
Oxidation of water
I2(s) e- → 2I v
Oxidation of I-
Reduction of water
2H2O + 2e- → 2H OH v
Zn e- → Zn(s) v
K e- → K(s) v

51. overpotential effect means water is here
Cl e- → 2Cl v
overpotential effect means water is here
1/2O2 + 2H+(10-7M) → H v
Oxidation of water
I2(s) e- → 2I v
Oxidation of I-
Reduction of water
2H2O + 2e- → 2H OH v
Zn e- → Zn(s) v
K e- → K(s) v

52. overpotential effect means water is here
Cl e- → 2Cl v
overpotential effect means water is here
1/2O2 + 2H+(10-7M) → H v
Oxidation of water
I2(s) e- → 2I v
Oxidation of I-
pick strongest reducing agent- lower
Reduction of water
2H2O + 2e- → 2H OH v
Zn e- → Zn(s) v
K e- → K(s) v

53. 2. Draw and completely analyze a 1.0 M KI electrolytic cell.
For oxidation the most spontaneous reaction is found on the redox chart and is lowest.
Power Source Pt -
Cathode
Reduction
2H2O+2e- → 2H2+ 2OH v +
Anode
Oxidation K+ I-
H2O

54. 2. Draw and completely analyze a 1.0 M KI electrolytic cell.
For oxidation the most spontaneous reaction is found on the redox chart and is lowest.
Power Source Pt -
Cathode
Reduction
2H2O+2e- → 2H2+ 2OH v +
Anode
Oxidation
2I- → I2(s) + 2e-
-0.54 v K+ I-
H2O

55. 2. Draw and completely analyze a 1.0 M KI electrolytic cell.
Write the overall reaction with the cell potential.
Power Source Pt -
Cathode
Reduction
2H2O +2e- → 2H2+ 2OH-
-0.41 v +
Anode
Oxidation
2I- → I2(s) + 2e-
-0.54 v K+ I-
H2O

56. 2. Draw and completely analyze a 1.0 M KI electrolytic cell.
Write the overall reaction with the cell potential.
Power Source Pt -
Cathode
Reduction
2H2O+2e- → 2H2+ 2OH v +
Anode
Oxidation
2I- → I2(s) + 2e-
-0.54 v K+ I-
H2O
2H2O+ 2I- → 2H2+ I2(s) + 2OH- E0 = v

57. 2. Draw and completely analyze a 1.0 M KI electrolytic cell.
Write the overall reaction with the cell potential.
Power Source e- e- Pt -
Cathode
Reduction
2H2O+2e- → H2+ 2OH v +
Anode
Oxidation
2I- → I2(s) + 2e-
-0.54 v K+ I-
H2O
2H2O+ 2I- → H2+ I2(s) + 2OH- E0 = v MTV = v