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

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 NaBr electrolytic cell.

Draw a beaker, two inert electrodes wired to a power supply.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Power Source - + Pt

2. Draw and completely analyze a 1.0 M KI electrolytic cell. Power Source - + Pt K+I-H2OK+I-H2O Add the ions. (aq) or M or solution means water.

2. Draw and completely analyze a 1.0 M KI electrolytic cell. Power Source - + Pt K+I-H2OK+I-H2O Label the -, +, anode, cathode, oxidation, and reduction.

2. Draw and completely analyze a 1.0 M KI electrolytic cell. Power Source - + Pt K+I-H2OK+I-H2O Label the -, +, anode, cathode, oxidation, and reduction. - Cathode reduction + Anode oxidation

2. Draw and completely analyze a 1.0 M KI electrolytic cell. Power Source - + Pt K+I-H2OK+I-H2O The cation and water migrate to the cathode - Cathode reduction + Anode oxidation

2. Draw and completely analyze a 1.0 M KI electrolytic cell. Power Source - + Pt K+I-H2OK+I-H2O The cation and water migrate to the cathode - Cathode reduction + Anode oxidation

2. Draw and completely analyze a 1.0 M KI electrolytic cell. Power Source - + Pt K+I-H2OK+I-H2O The cation or water reduces. The higher one on the chart is most spontaneous and occurs. - Cathode reduction + Anode oxidation

Cl 2 + 2e- → 2Cl-1.36 v 1/2O 2 + 2H + (10 -7 M) + 2e - → H v 2H 2 O + 2e - → 2H 2 + 2OH v Zn e - → Zn (s) v K + + 1e - → K (s) v

Cl 2 + 2e - → 2Cl-1.36 v 1/2O 2 + 2H + (10 -7 M) → H v Reduction of water 2H 2 O + 2e - → 2H 2 + 2OH v Zn e - → Zn (s) v K + + 1e - → K (s) v

Cl 2 + 2e - → 2Cl-1.36 v 1/2O 2 + 2H + (10 -7 M) → H v Oxidation of water Reduction of water 2H 2 O + 2e - → 2H 2 + 2OH v Zn e - → Zn (s) v K + + 1e - → K (s) v

Cl 2 + 2e - → 2Cl-1.36 v 1/2O 2 + 2H + (10 -7 M) → H v Oxidation of water Reduction of water 2H 2 O + 2e - → 2H 2 + 2OH v Zn e - → Zn (s) v Reduction of K + K + + 1e - → K (s) v

Cl 2 + 2e - → 2Cl-1.36 v 1/2O 2 + 2H + (10 -7 M) → H v Oxidation of water strongest oxidizing agent or highest Reduction of waterselect most spontaneous reaction 2H 2 O + 2e - → 2H 2(g) + 2OH v Zn e - → Zn (s) v Reduction of K K + + 1e - → K (s) v Overpotential Effect- treat water as if it were just below Zn

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. Power Source - + Pt K+I-H2OK+I-H2O The cation or water reduces. The higher one on the chart is most spontaneous and occurs. - Cathode Reduction + Anode oxidation

2. Draw and completely analyze a 1.0 M KI electrolytic cell. Power Source - + Pt K+I-H2OK+I-H2O The cation or water reduces. The higher one on the chart is most spontaneous and occurs. - Cathode Reduction 2H 2 O+2e - → 2H 2 + 2OH v + Anode oxidation

2. Draw and completely analyze a 1.0 M KI electrolytic cell. Power Source - + Pt K+I-H2OK+I-H2O The anion + water goes to the anode. + Anode oxidation - Cathode Reduction 2H 2 O+2e - → 2H 2 + 2OH v

2. Draw and completely analyze a 1.0 M KI electrolytic cell. Power Source - + Pt K+I-H2OK+I-H2O For oxidation the most spontaneous reaction is found on the redox chart and is lowest. + Anode oxidation - Cathode Reduction 2H 2 O+2e - → 2H 2 + 2OH v

Cl 2 + 2e- → 2Cl-1.36 v 1/2O 2 + 2H + (10 -7 M) + 2e - → H v Oxidation of water I 2(s) + 2e - → 2I v Reduction of water 2H 2 O + 2e - → 2H 2 + 2OH v Zn e - → Zn (s) v K + + 1e - → K (s) v

Cl 2 + 2e- → 2Cl-1.36 v 1/2O 2(g) + 2H + (10 -7 M) → H v Oxidation of water I 2(s) + 2e - → 2I v Oxidation of I - Reduction of water 2H 2 O + 2e - → 2H 2 + 2OH v Zn e - → Zn (s) v K + + 1e - → K (s) v

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

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

2. Draw and completely analyze a 1.0 M KI electrolytic cell. Power Source - + Pt K+I-H2OK+I-H2O For oxidation the most spontaneous reaction is found on the redox chart and is lowest. + Anode Oxidation - Cathode Reduction 2H 2 O+2e - → 2H 2 + 2OH v

2. Draw and completely analyze a 1.0 M KI electrolytic cell. Power Source - + Pt K+I-H2OK+I-H2O For oxidation the most spontaneous reaction is found on the redox chart and is lowest. + Anode Oxidation 2I - → I 2(s) + 2e v - Cathode Reduction 2H 2 O+2e - → 2H 2 + 2OH v

2. Draw and completely analyze a 1.0 M KI electrolytic cell. Power Source - + Pt K+I-H2OK+I-H2O Write the overall reaction with the cell potential. + Anode Oxidation 2I - → I 2(s) + 2e v - Cathode Reduction 2H 2 O +2e - → 2H 2 + 2OH v

2. Draw and completely analyze a 1.0 M KI electrolytic cell. Power Source - + Pt K+I-H2OK+I-H2O Write the overall reaction with the cell potential. + Anode Oxidation 2I - → I 2(s) + 2e v - Cathode Reduction 2H 2 O+2e - → 2H 2 + 2OH v 2H 2 O+ 2I - → 2H 2 + I 2(s) + 2OH - E 0 = v

2. Draw and completely analyze a 1.0 M KI electrolytic cell. Power Source - + Pt K+I-H2OK+I-H2O Write the overall reaction with the cell potential. + Anode Oxidation 2I - → I 2(s) + 2e v - Cathode Reduction 2H 2 O+2e - → H 2 + 2OH v 2H 2 O+ 2I - → H 2 + I 2(s) + 2OH - E 0 = v MTV = +0.95v e-e- e-e-