Notes on Electrolytic Cells An electrolytic cell is

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. 2. 3. Nonspontaneous redox reaction Produces chemicals from electricity Forces electrolysis to occur

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.

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.

1. Draw and completely analyze a molten Na. Br electrolytic cell.

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

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

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

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

1. Draw and completely analyze a molten Na. Br electrolytic cell. Power Supply DC + Pt Add the electrolyte Pt

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

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

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

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

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

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

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

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

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

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

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

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

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

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

1. Draw and completely analyze a molten Na. Br electrolytic cell. The potential for Power Source each half reaction + is listed and the oxidation sign is reversed Pt Pt _ reduction cathode 2 Na+ + 2 e- → 2 Na(l) -2. 71 v Na+ Br- + oxidation anode 2 Br- → Br 2(g)+ 2 e-1. 09 v

1. Draw and completely analyze a molten Na. Br electrolytic cell. The overall redox Power Source reaction is written. - + Pt Pt _ reduction cathode 2 Na+ + 2 e- → 2 Na(l) -2. 71 v Na+ Br- + oxidation anode 2 Br- → Br 2(g)+ 2 e-1. 09 v

1. Draw and completely analyze a molten Na. Br electrolytic cell. The overall redox Power Source reaction is written. - + Pt Pt _ reduction cathode 2 Na+ + 2 e- → 2 Na(l) -2. 71 v Na+ Br- 2 Na+ + 2 Br- → Br 2(g)+ 2 Na(l) + oxidation anode 2 Br- → Br 2(g)+ 2 e-1. 09 v E 0 = -3. 80 v

1. Draw and completely analyze a molten Na. Br The minimum theoretical electrolytic cell. Power Source + voltage MTV required to force this nonspontaneous reaction to occur is the negative of the cell potential. Pt Pt _ reduction cathode 2 Na+ + 2 e- → 2 Na(l) -2. 71 v Na+ Br- + oxidation anode 2 Br- → Br 2(g)+ 2 e-1. 09 v 2 Na+ + 2 Br- → Br 2(g)+ 2 Na(s) E 0 = -3. 80 v

1. Draw and completely analyze a molten Na. Br The minimum theoretical electrolytic cell. Power Source + Pt Pt _ reduction cathode 2 Na+ + 2 e- → 2 Na(l) -2. 71 v 2 Na+ + 2 Br- → Br 2(g)+ 2 Na(s) voltage MTV required to force this nonspontaneous reaction to occur is the negative of the cell potential. Na+ Br- + oxidation anode 2 Br- → Br 2(g)+ 2 e-1. 09 v E 0 = -3. 80 v MTV = +3. 80 v

1. Draw and completely analyze a molten Na. Br Electrons flow through electrolytic cell. Power Source + Pt Pt _ reduction cathode 2 Na+ + 2 e- → 2 Na(l) -2. 71 v 2 Na+ + 2 Br- → Br 2(g)+ 2 Na(s) the wire from anode to cathode. Na+ Br- + oxidation anode 2 Br- → Br 2(g)+ 2 e-1. 09 v E 0 = -3. 80 v MTV = +3. 80 v

1. Draw and completely analyze a molten Na. Br Electrons flow through electrolytic cell. e- the wire from anode to cathode. Power Source + e. Pt Pt _ reduction cathode 2 Na+ + 2 e- → 2 Na(l) -2. 71 v 2 Na+ + 2 Br- → Br 2(g)+ 2 Na(s) Na+ Br- + oxidation anode 2 Br- → Br 2(g)+ 2 e-1. 09 v E 0 = -3. 80 v MTV = +3. 80 v

2. Draw and completely analyze a 1. 0 M KI electrolytic cell.

2. Draw and completely analyze a 1. 0 M KI electrolytic cell. Power Source + Pt Pt

2. Draw and completely analyze a 1. 0 M KI electrolytic cell. Power Source + Add the ions. (aq) or M or solution means water. Pt Pt K+ IH 2 O

2. Draw and completely analyze a 1. 0 M KI electrolytic cell. Label the -, +, anode, cathode, Power Source + oxidation, and reduction. Pt Pt K+ IH 2 O

2. Draw and completely analyze a 1. 0 M KI electrolytic cell. Label the -, +, anode, cathode, Power Source + oxidation, and reduction. Pt Pt Cathode reduction K+ IH 2 O + Anode oxidation

2. Draw and completely analyze a 1. 0 M KI electrolytic cell. The cation and water migrate to the Power Source + cathode Pt Pt Cathode reduction K+ IH 2 O + Anode oxidation

2. Draw and completely analyze a 1. 0 M KI electrolytic cell. The cation and water migrate to the Power Source + cathode Pt Pt Cathode reduction K+ IH 2 O + Anode oxidation

2. Draw and completely analyze a 1. 0 M KI electrolytic cell. The cation or water reduces. The higher Power Source + one on the chart is most spontaneous and occurs. Pt Pt Cathode reduction K+ IH 2 O + Anode oxidation

Cl 2 + 1/2 O 2 + 2 e- → 2 Cl- 2 H+(10 -7 M) + 2 e- 2 H 2 O + 2 e- 1. 36 v → H 20 → 2 H 2 + 2 OH- -0. 42 v Zn 2+ + 2 e- → Zn(s) -0. 76 v K+ + 1 e- → -2. 93 v K(s) 0. 82 v

Cl 2 + 1/2 O 2 + 2 e- → 2 Cl- 1. 36 v 2 H+(10 -7 M) → H 20 0. 32 v Reduction of water 2 H 2 O + 2 e- → 2 H 2 + 2 OH- -0. 42 v Zn 2+ + 2 e- → Zn(s) -0. 76 v K+ + 1 e- → -2. 93 v K(s)

Cl 2 + 2 e- → 2 Cl- 1. 36 v 1/2 O 2 + 2 H+(10 -7 M) → H 20 0. 32 v Oxidation of water Reduction of water 2 H 2 O + 2 e- → 2 H 2 + 2 OH- -0. 42 v Zn 2+ + 2 e- → Zn(s) -0. 76 v K+ + 1 e- → -2. 93 v K(s)

Cl 2 + 2 e- → 2 Cl- 1. 36 v 1/2 O 2 + 2 H+(10 -7 M) → H 20 0. 32 v Oxidation of water Reduction of water 2 H 2 O + 2 e- Zn 2+ Reduction of K+ K+ + + 2 e- 1 e- → → 2 H 2 + 2 OH- -0. 42 v → Zn(s) -0. 76 v K(s) -2. 93 v

Cl 2 + 2 e- → 2 Cl- 1/2 O 2 + 2 H+(10 -7 M) 1. 36 v → H 20 0. 32 v Oxidation of water strongest oxidizing agent or highest select most spontaneous reaction Reduction of water 2 H 2 O + 2 e- → 2 H 2(g) + 2 OH- -0. 42 v Overpotential Effect- treat water as if it were just below Zn Zn 2+ Reduction of K K+ + 2 e- → Zn(s) -0. 76 v + 1 e- → -2. 93 v K(s)

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.

2. Draw and completely analyze a 1. 0 M KI electrolytic cell. The cation or water reduces. The higher Power Source + one on the chart is most spontaneous and occurs. Pt Pt Cathode Reduction K+ IH 2 O + Anode oxidation

2. Draw and completely analyze a 1. 0 M KI electrolytic cell. The cation or water reduces. The higher Power Source + one on the chart is most spontaneous and occurs. Pt Pt Cathode Reduction 2 H 2 O+2 e- → 2 H 2+ 2 OH-0. 41 v K+ IH 2 O + Anode oxidation

2. Draw and completely analyze a 1. 0 M KI electrolytic cell. The anion + water goes to the anode. Power Source - + Pt Pt Cathode Reduction 2 H 2 O+2 e- → 2 H 2+ 2 OH-0. 41 v K+ IH 2 O + Anode oxidation

2. Draw and completely analyze a 1. 0 M KI electrolytic cell. For oxidation the most spontaneous Power Source + reaction is found on the redox chart and is lowest. Pt Pt Cathode Reduction 2 H 2 O+2 e- → 2 H 2+ 2 OH-0. 41 v K+ IH 2 O + Anode oxidation

Cl 2 + 2 e- → 2 Cl- 1. 36 v 1/2 O 2 + 2 H+(10 -7 M) + 2 e- → H 20 0. 82 v Oxidation of water I 2(s) + 2 e- → 2 I- 0. 54 v → 2 H 2 + 2 OH- -0. 42 v Reduction of water 2 H 2 O + 2 e- Zn 2+ + 2 e- → Zn(s) -0. 76 v K+ + 1 e- → -2. 93 v K(s)

Cl 2 + 2 e- → 2 Cl- 1. 36 v 1/2 O 2(g) + 2 H+(10 -7 M) → H 20 0. 82 v Oxidation of water I 2(s) 2 I 0. 54 v Oxidation of I- + 2 e- → Reduction of water 2 H 2 O + 2 e- → 2 H 2 + 2 OH- -0. 42 v Zn 2+ + 2 e- → Zn(s) -0. 76 v K+ + 1 e- → -2. 93 v K(s)

Cl 2 + 2 e- → 2 Cl 1. 36 v overpotential effect means water is here 1/2 O 2 + 2 H+(10 -7 M) → H 20 0. 82 v Oxidation of water I 2(s) 2 I 0. 54 v Oxidation of I- + 2 e- → Reduction of water 2 H 2 O + 2 e- → 2 H 2 + 2 OH- -0. 42 v Zn 2+ + 2 e- → Zn(s) -0. 76 v K+ + 1 e- → -2. 93 v K(s)

Cl 2 + 2 e- → 2 Cl 1. 36 v overpotential effect means water is here 1/2 O 2 + 2 H+(10 -7 M) → I 2(s) + 2 e- H 20 0. 82 v Oxidation of water → 2 I 0. 54 v Oxidation of Ipick strongest reducing agent- lower Reduction of water 2 H 2 O + 2 e- → 2 H 2 + 2 OH- -0. 42 v Zn 2+ + 2 e- → Zn(s) -0. 76 v K+ + 1 e- → -2. 93 v K(s)

2. Draw and completely analyze a 1. 0 M KI electrolytic cell. For oxidation the most spontaneous Power Source + reaction is found on the redox chart and is lowest. Pt Pt Cathode Reduction 2 H 2 O+2 e- → 2 H 2+ 2 OH-0. 41 v K+ IH 2 O + Anode Oxidation

2. Draw and completely analyze a 1. 0 M KI electrolytic cell. For oxidation the most spontaneous Power Source + reaction is found on the redox chart and is lowest. Pt Pt Cathode Reduction 2 H 2 O+2 e- → 2 H 2+ 2 OH-0. 41 v K+ IH 2 O + Anode Oxidation 2 I- → I 2(s) + 2 e-0. 54 v

2. Draw and completely analyze a 1. 0 M KI electrolytic cell. Write the overall reaction with the Power Source + cell potential. Pt Pt Cathode Reduction 2 H 2 O +2 e- → 2 H 2+ 2 OH-0. 41 v K+ IH 2 O + Anode Oxidation 2 I- → I 2(s) + 2 e-0. 54 v

2. Draw and completely analyze a 1. 0 M KI electrolytic cell. Write the overall reaction with the Power Source + cell potential. Pt Pt Cathode Reduction 2 H 2 O+2 e- → 2 H 2+ 2 OH-0. 41 v K+ IH 2 O 2 H 2 O+ 2 I- → 2 H 2+ I 2(s) + 2 OH- + Anode Oxidation 2 I- → I 2(s) + 2 e-0. 54 v E 0 = -0. 95 v

2. Draw and completely analyze a 1. 0 M KI electrolytic cell. Write the overall reaction with the Power Source + ecell potential. e. Pt Pt Cathode Reduction 2 H 2 O+2 e- → H 2+ 2 OH-0. 41 v + Anode Oxidation K+ IH 2 O 2 H 2 O+ 2 I- → H 2+ I 2(s) + 2 OH- 2 I- → I 2(s) + 2 e-0. 54 v E 0 = -0. 95 v MTV = +0. 95 v