chem 5013 applied chemical principles chapter thirteen professor bensley alfred state college
TRANSCRIPT
CHEM 5013 CHEM 5013 Applied Chemical Applied Chemical
PrinciplesPrinciples
Chapter ThirteenChapter Thirteen
Professor BensleyProfessor BensleyAlfred State CollegeAlfred State College
Chapter ObjectivesChapter Objectives
Define oxidation and reduction.Define oxidation and reduction. Write and balance half-reactions for Write and balance half-reactions for
simple redox processes.simple redox processes. Describe the differences between Describe the differences between
galvanic and electrolytic cells.galvanic and electrolytic cells. Use standard reduction potentials to Use standard reduction potentials to
calculate cell potentials under calculate cell potentials under standard conditions.standard conditions.
Chapter ObjectivesChapter Objectives
Use standard reduction potentials to Use standard reduction potentials to predict the spontaneous direction of predict the spontaneous direction of a redox reaction.a redox reaction.
Calculate the amount of metal Calculate the amount of metal plated, the amount of current plated, the amount of current needed, or the time required for an needed, or the time required for an electrolysis process.electrolysis process.
Chapter ObjectivesChapter Objectives
Distinguish between primary and Distinguish between primary and secondary batteries.secondary batteries.
Describe the chemistry of some Describe the chemistry of some common battery types and explain common battery types and explain why each type of battery is suitable why each type of battery is suitable for a particular application.for a particular application.
Describe at least two common Describe at least two common techniques for preventing corrosion.techniques for preventing corrosion.
Oxidation / ReductionOxidation / Reduction
Oxidation/Reduction Reaction (Redox):
Oxidation:
Reduction:
Oxidation Numbers:
Rule #
Applies To Statement
1 Elements Oxidation number of an element is ALWAYS zero (0).
2 Compounds The sum of the oxidation numbers of the atoms in a compound is ALWAYS zero (0).
3 Monatomic Ions
Oxidation number of a monatomic ion is ALWAYS equal to the charge on the ion.
4 Polyatomic Ions
The sum of the oxidations numbers of the atoms in a polyatomic ion equals the charge on the ion.
5 Oxygen The oxidation number of oxygen is -2 when it is in a compound or a polyatomic ion.
6 Hydrogen The oxidation number of hydrogen is +1 when it is in a compound or a polyatomic ion.
7 Halogens The oxidation number of halogen atoms is -1 when found in a compound or polyatomic ion unless it is combined with oxygen.
Oxidation NumbersOxidation Numbers
Assign oxidation numbers to Carbon in each of Assign oxidation numbers to Carbon in each of the following compounds:the following compounds:
1. Carbon Monoxide1. Carbon Monoxide 2. Carbon Dioxide2. Carbon Dioxide
3. C3. C66HH1212OO66 4. Sodium 4. Sodium BicarbonateBicarbonate
Redox Half-ReactionsRedox Half-Reactions What happens when copper wire is placed in a What happens when copper wire is placed in a
silver nitrate solution? 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 What are the crystals forming on the surface of the
copper wire?copper wire?
Reducing and Oxidizing Reducing and Oxidizing AgentsAgents
0 +1 +2 0Cu(s) + 2Ag+ (aq) Cu2+ (aq) + 2Ag
(s)
Oxidation
Reduction
Reducing Agent
Oxidizing Agent
Reducing Agent:Reducing Agent:
Oxidizing Agent:Oxidizing Agent:
Galvanic Cell TerminologyGalvanic Cell Terminology
Salt Bridge:Salt Bridge:
Electrodes:Electrodes:
Anode: Anode:
Cathode:Cathode:
anode | anode electrolyte || cathode electrolyte | cathode
Galvanic Cell TerminologyGalvanic Cell Terminology
Cell notation:
EMF (electromotive force) or cell potential:
E0 (cell) =
Cell PotentialsCell Potentials1.1. Calculate the cell potential for the previous Calculate the cell potential for the previous
Copper/Silver cell.Copper/Silver cell.
2.2. Calculate the cell potential for the following Calculate the cell potential for the following galvanic cell.galvanic cell.
Fe(s) | Fe2+ (aq) (1.0M) || Cu 2+ (aq) | Cu (s)
Primary CellsPrimary Cells
Dry Cell Dry Cell BatteryBattery
1.5 Volts 1.5 Volts Has a finite life Has a finite life
even when not even when not used since used since acidic NHacidic NH44Cl Cl corrodes cancorrodes can
Primary CellsPrimary Cells
Alkaline Dry Alkaline Dry Cell Cell
1.5 Volts 1.5 Volts Longer life Longer life
than dry cell than dry cell but more but more expensiveexpensive
Primary CellsPrimary Cells
Lithium – Lithium – Iodine Battery Iodine Battery
High High resistance, low resistance, low currentcurrent
Used in Used in pacemakers pacemakers and is very and is very reliable (10 reliable (10 yrs)yrs)
Secondary CellsSecondary Cells
Nickel-Nickel-Cadmium Cadmium (NiCad)(NiCad)
Used in Used in calculators, calculators, power tools, power tools, shavers, etc.shavers, etc.
Rechargeable Rechargeable and light.and light.
Secondary CellsSecondary Cells
Lead Storage Lead Storage Cell Cell
Car battery - Car battery - rechargeablerechargeable
Single cell is Single cell is 2V, 6 cells in a 2V, 6 cells in a row so overall row so overall is approx. 12 Vis approx. 12 V
Electrochemistry Electrochemistry ApplicationsApplications
Fuel CellFuel Cell Continuous supply Continuous supply
of fuelof fuel Anode-hydrogen Anode-hydrogen
gas, Cathode-gas, Cathode-oxygen gasoxygen gas
VERY efficientVERY efficient Storage and Storage and
transport of transport of Hydrogen is Hydrogen is limitation.limitation. 2 H2 (g) + O2 (g) 2 H2O (l)
Electrochemistry Electrochemistry ApplicationsApplications
Corrosion – rust – forms only in the Corrosion – rust – forms only in the presence of Opresence of O22 and H and H22O.O.
Active Electrolysis and Active Electrolysis and ElectroplatingElectroplating
Electroplating:Electroplating:
Electrochemical reactions involved in Electrochemical reactions involved in the plating of silverthe plating of silver
Anode:Anode:
Cathode:Cathode:
Ag(s) + 2 CN-(aq) Ag(CN)2- (aq) + e-
Ag(CN)2- (aq) + e- Ag(s) + 2 CN-(aq)
ElectroplatingElectroplating Current:Current:
The unit of current, the ampere (A), is The unit of current, the ampere (A), is defined as one coulomb per second: defined as one coulomb per second:
1 A = 1 C / s1 A = 1 C / s
Charge = current time
Q = I t
Current and ChargeCurrent and Charge
Faraday’s constant: Faraday’s constant: F = 96,485 C/molF = 96,485 C/mol
Use charge, Faraday’s Constant, and # moles of Use charge, Faraday’s Constant, and # moles of electrons to determine mass of metal plated on object.electrons to determine mass of metal plated on object.
In a copper plating experiment in which copper metal is In a copper plating experiment in which copper metal is deposited from copper(II) ion solution, the system is run for 2.6 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 hours at a current of 12.0 A. What mass of copper is deposited?deposited?