CHEM 5013 Applied Chemical Principles Chapter Thirteen Professor Bensley Alfred State College

Chapter Objectives Define oxidation and reduction. Define oxidation and reduction. Write and balance half-reactions for simple redox processes. Write and balance half-reactions for simple redox processes. Describe the differences between galvanic and electrolytic cells. Describe the differences between galvanic and electrolytic cells. Use standard reduction potentials to calculate cell potentials under standard conditions. Use standard reduction potentials to calculate cell potentials under standard conditions.

Chapter Objectives Use standard reduction potentials to predict the spontaneous direction of a redox reaction. Use standard reduction potentials to predict the spontaneous direction of a redox reaction. Calculate the amount of metal plated, the amount of current needed, or the time required for an electrolysis process. Calculate the amount of metal plated, the amount of current needed, or the time required for an electrolysis process.

Chapter Objectives Distinguish between primary and secondary batteries. Distinguish between primary and secondary batteries. Describe the chemistry of some common battery types and explain why each type of battery is suitable for a particular application. Describe the chemistry of some common battery types and explain why each type of battery is suitable for a particular application. Describe at least two common techniques for preventing corrosion. Describe at least two common techniques for preventing corrosion.

Oxidation / Reduction Oxidation/Reduction Reaction (Redox): Oxidation: Reduction: Oxidation Numbers:

Rule #Applies ToStatement 1ElementsOxidation number of an element is ALWAYS zero (0). 2CompoundsThe sum of the oxidation numbers of the atoms in a compound is ALWAYS zero (0). 3Monatomic Ions Oxidation number of a monatomic ion is ALWAYS equal to the charge on the ion. 4Polyatomic IonsThe sum of the oxidations numbers of the atoms in a polyatomic ion equals the charge on the ion. 5OxygenThe oxidation number of oxygen is -2 when it is in a compound or a polyatomic ion. 6HydrogenThe oxidation number of hydrogen is +1 when it is in a compound or a polyatomic ion. 7HalogensThe oxidation number of halogen atoms is -1 when found in a compound or polyatomic ion unless it is combined with oxygen.

Oxidation Numbers Assign oxidation numbers to Carbon in each of the following compounds: 1. Carbon Monoxide2. Carbon Dioxide 3. C 6 H 12 O 6 4. Sodium Bicarbonate

Redox Half-Reactions What happens when copper wire is placed in a silver nitrate solution? What happens when copper wire is placed in a silver nitrate solution? The solution’s blue color is indicative of what in solution? The solution’s blue color is indicative of what in solution? What are the crystals forming on the surface of the copper wire? What are the crystals forming on the surface of the copper wire?

Reducing and Oxidizing Agents Cu(s) + 2Ag + (aq)  Cu 2+ (aq) + 2Ag (s) Oxidation Reduction Reducing Agent Oxidizing Agent Reducing Agent: Reducing Agent: Oxidizing Agent: Oxidizing Agent:

Building a Galvanic Cell Galvanic cell: Galvanic cell:

Galvanic Cell Terminology Salt Bridge: Salt Bridge: Electrodes: Electrodes: Anode: Anode: Cathode: Cathode:

Galvanic Cell Terminology Cell notation: EMF (electromotive force) or cell potential: E 0 (cell) =

Cell Potentials 1. Calculate the cell potential for the previous Copper/Silver cell. 2. Calculate the cell potential for the following galvanic cell. Fe(s) | Fe 2+ (aq) (1.0M) || Cu 2+ (aq) | Cu (s)

Batteries Battery: Primary Cells: Secondary Cells:

Primary Cells Dry Cell Battery Dry Cell Battery 1.5 Volts 1.5 Volts Has a finite life even when not used since acidic NH 4 Cl corrodes can Has a finite life even when not used since acidic NH 4 Cl corrodes can

Primary Cells Alkaline Dry Cell Alkaline Dry Cell 1.5 Volts 1.5 Volts Longer life than dry cell but more expensive Longer life than dry cell but more expensive

Primary Cells Lithium – Iodine Battery Lithium – Iodine Battery High resistance, low current High resistance, low current Used in pacemakers and is very reliable (10 yrs) Used in pacemakers and is very reliable (10 yrs)

Secondary Cells Nickel-Cadmium (NiCad) Nickel-Cadmium (NiCad) Used in calculators, power tools, shavers, etc. Used in calculators, power tools, shavers, etc. Rechargeable and light. Rechargeable and light.

Secondary Cells Lead Storage Cell Lead Storage Cell Car battery - rechargeable Car battery - rechargeable Single cell is 2V, 6 cells in a row so overall is approx. 12 V Single cell is 2V, 6 cells in a row so overall is approx. 12 V

Electrochemistry Applications Fuel Cell Fuel Cell Continuous supply of fuel Continuous supply of fuel Anode-hydrogen gas, Cathode-oxygen gas Anode-hydrogen gas, Cathode-oxygen gas VERY efficient VERY efficient Storage and transport of Hydrogen is limitation. Storage and transport of Hydrogen is limitation. 2 H 2 (g) + O 2 (g)  2 H 2 O (l)

Electrochemistry Applications Corrosion – rust – forms only in the presence of O 2 and H 2 O. Corrosion – rust – forms only in the presence of O 2 and H 2 O.

Electrochemistry Applications Galvanizing: Cathodic Protection:

Electrolysis Electrolysis: Passive electrolysis: Active electrolysis:

Active Electrolysis and Electroplating Electroplating: Electroplating: Electrochemical reactions involved in the plating of silver Electrochemical reactions involved in the plating of silver Anode: Anode: Cathode: Cathode:

Electroplating Current: Current: The unit of current, the ampere (A), is defined as one coulomb per second: The unit of current, the ampere (A), is defined as one coulomb per second: 1 A = 1 C / s

Current and Charge Faraday’s constant: F = 96,485 C/mol Faraday’s constant: F = 96,485 C/mol Use charge, Faraday’s Constant, and # moles of electrons to determine mass of metal plated on object. Use charge, Faraday’s Constant, and # moles of electrons to determine mass of metal plated on object. In a copper plating experiment in which copper metal is deposited from copper(II) ion solution, the system is run for 2.6 hours at a current of 12.0 A. What mass of copper is deposited? In a copper plating experiment in which copper metal is deposited from copper(II) ion solution, the system is run for 2.6 hours at a current of 12.0 A. What mass of copper is deposited?