Raffi Hovasapian

Raffi Hovasapian

Potential, Work, & Free Energy

Slide Duration:

Table of Contents

Section 1: Review
Naming Compounds

41m 24s

Intro
0:00
Periodic Table of Elements
0:15
Naming Compounds
3:13
Definition and Examples of Ions
3:14
Ionic (Symbol to Name): NaCl
5:23
Ionic (Name to Symbol): Calcium Oxide
7:58
Ionic - Polyatoms Anions: Examples
12:45
Ionic - Polyatoms Anions (Symbol to Name): KClO
14:50
Ionic - Polyatoms Anions (Name to Symbol): Potassium Phosphate
15:49
Ionic Compounds Involving Transition Metals (Symbol to Name): Co₂(CO₃)₃
20:48
Ionic Compounds Involving Transition Metals (Name to Symbol): Palladium 2 Acetate
22:44
Naming Covalent Compounds (Symbol to Name): CO
26:21
Naming Covalent Compounds (Name to Symbol): Nitrogen Trifluoride
27:34
Naming Covalent Compounds (Name to Symbol): Dichlorine Monoxide
27:57
Naming Acids Introduction
28:11
Naming Acids (Name to Symbol): Chlorous Acid
35:08
% Composition by Mass Example
37:38
Stoichiometry

37m 19s

Intro
0:00
Stoichiometry
0:25
Introduction to Stoichiometry
0:26
Example 1
5:03
Example 2
10:17
Example 3
15:09
Example 4
24:02
Example 5: Questions
28:11
Example 5: Part A - Limiting Reactant
30:30
Example 5: Part B
32:27
Example 5: Part C
35:00
Section 2: Aqueous Reactions & Stoichiometry
Precipitation Reactions

31m 14s

Intro
0:00
Precipitation Reactions
0:53
Dissociation of ionic Compounds
0:54
Solubility Guidelines for ionic Compounds: Soluble Ionic Compounds
8:15
Solubility Guidelines for ionic Compounds: Insoluble ionic Compounds
12:56
Precipitation Reactions
14:08
Example 1: Mixing a Solution of BaCl₂ & K₂SO₄
21:21
Example 2: Mixing a Solution of Mg(NO₃)₂ & KI
26:10
Acid-Base Reactions

43m 21s

Intro
0:00
Acid-Base Reactions
1:00
Introduction to Acid: Monoprotic Acid and Polyprotic Acid
1:01
Introduction to Base
8:28
Neutralization
11:45
Example 1
16:17
Example 2
21:55
Molarity
24:50
Example 3
26:50
Example 4
30:01
Example 4: Limiting Reactant
37:51
Example 4: Reaction Part
40:01
Oxidation Reduction Reactions

47m 58s

Intro
0:00
Oxidation Reduction Reactions
0:26
Oxidation and Reduction Overview
0:27
How Can One Tell Whether Oxidation-Reduction has Taken Place?
7:13
Rules for Assigning Oxidation State: Number 1
11:22
Rules for Assigning Oxidation State: Number 2
12:46
Rules for Assigning Oxidation State: Number 3
13:25
Rules for Assigning Oxidation State: Number 4
14:50
Rules for Assigning Oxidation State: Number 5
15:41
Rules for Assigning Oxidation State: Number 6
17:00
Example 1: Determine the Oxidation State of Sulfur in the Following Compounds
18:20
Activity Series and Reduction Properties
25:32
Activity Series and Reduction Properties
25:33
Example 2: Write the Balance Molecular, Total Ionic, and Net Ionic Equations for Al + HCl
31:37
Example 3
34:25
Example 4
37:55
Stoichiometry Examples

31m 50s

Intro
0:00
Stoichiometry Example 1
0:36
Example 1: Question and Answer
0:37
Stoichiometry Example 2
6:57
Example 2: Questions
6:58
Example 2: Part A Solution
12:16
Example 2: Part B Solution
13:05
Example 2: Part C Solution
14:00
Example 2: Part D Solution
14:38
Stoichiometry Example 3
17:56
Example 3: Questions
17:57
Example 3: Part A Solution
19:51
Example 3: Part B Solution
21:43
Example 3: Part C Solution
26:46
Section 3: Gases
Pressure, Gas Laws, & The Ideal Gas Equation

49m 40s

Intro
0:00
Pressure
0:22
Pressure Overview
0:23
Torricelli: Barometer
4:35
Measuring Gas Pressure in a Container
7:49
Boyle's Law
12:40
Example 1
16:56
Gas Laws
21:18
Gas Laws
21:19
Avogadro's Law
26:16
Example 2
31:47
Ideal Gas Equation
38:20
Standard Temperature and Pressure (STP)
38:21
Example 3
40:43
Partial Pressure, Mol Fraction, & Vapor Pressure

32m

Intro
0:00
Gases
0:27
Gases
0:28
Mole Fractions
5:52
Vapor Pressure
8:22
Example 1
13:25
Example 2
22:45
Kinetic Molecular Theory and Real Gases

31m 58s

Intro
0:00
Kinetic Molecular Theory and Real Gases
0:45
Kinetic Molecular Theory 1
0:46
Kinetic Molecular Theory 2
4:23
Kinetic Molecular Theory 3
5:42
Kinetic Molecular Theory 4
6:27
Equations
7:52
Effusion
11:15
Diffusion
13:30
Example 1
19:54
Example 2
23:23
Example 3
26:45
AP Practice for Gases

25m 34s

Intro
0:00
Example 1
0:34
Example 1
0:35
Example 2
6:15
Example 2: Part A
6:16
Example 2: Part B
8:46
Example 2: Part C
10:30
Example 2: Part D
11:15
Example 2: Part E
12:20
Example 2: Part F
13:22
Example 3
14:45
Example 3
14:46
Example 4
18:16
Example 4
18:17
Example 5
21:04
Example 5
21:05
Section 4: Thermochemistry
Energy, Heat, and Work

37m 32s

Intro
0:00
Thermochemistry
0:25
Temperature and Heat
0:26
Work
3:07
System, Surroundings, Exothermic Process, and Endothermic Process
8:19
Work & Gas: Expansion and Compression
16:30
Example 1
24:41
Example 2
27:47
Example 3
31:58
Enthalpy & Hess's Law

32m 34s

Intro
0:00
Thermochemistry
1:43
Defining Enthalpy & Hess's Law
1:44
Example 1
6:48
State Function
13:11
Example 2
17:15
Example 3
24:09
Standard Enthalpies of Formation

23m 9s

Intro
0:00
Thermochemistry
1:04
Standard Enthalpy of Formation: Definition & Equation
1:05
∆H of Formation
10:00
Example 1
11:22
Example 2
19:00
Calorimetry

39m 28s

Intro
0:00
Thermochemistry
0:21
Heat Capacity
0:22
Molar Heat Capacity
4:44
Constant Pressure Calorimetry
5:50
Example 1
12:24
Constant Volume Calorimetry
21:54
Example 2
24:40
Example 3
31:03
Section 5: Kinetics
Reaction Rates and Rate Laws

36m 24s

Intro
0:00
Kinetics
2:18
Rate: 2 NO₂ (g) → 2NO (g) + O₂ (g)
2:19
Reaction Rates Graph
7:25
Time Interval & Average Rate
13:13
Instantaneous Rate
15:13
Rate of Reaction is Proportional to Some Power of the Reactant Concentrations
23:49
Example 1
27:19
Method of Initial Rates

30m 48s

Intro
0:00
Kinetics
0:33
Rate
0:34
Idea
2:24
Example 1: NH₄⁺ + NO₂⁻ → NO₂ (g) + 2 H₂O
5:36
Example 2: BrO₃⁻ + 5 Br⁻ + 6 H⁺ → 3 Br₂ + 3 H₂O
19:29
Integrated Rate Law & Reaction Half-Life

32m 17s

Intro
0:00
Kinetics
0:52
Integrated Rate Law
0:53
Example 1
6:26
Example 2
15:19
Half-life of a Reaction
20:40
Example 3: Part A
25:41
Example 3: Part B
28:01
Second Order & Zero-Order Rate Laws

26m 40s

Intro
0:00
Kinetics
0:22
Second Order
0:23
Example 1
6:08
Zero-Order
16:36
Summary for the Kinetics Associated with the Reaction
21:27
Activation Energy & Arrhenius Equation

40m 59s

Intro
0:00
Kinetics
0:53
Rate Constant
0:54
Collision Model
2:45
Activation Energy
5:11
Arrhenius Proposed
9:54
2 Requirements for a Successful Reaction
15:39
Rate Constant
17:53
Arrhenius Equation
19:51
Example 1
25:00
Activation Energy & the Values of K
32:12
Example 2
36:46
AP Practice for Kinetics

29m 8s

Intro
0:00
Kinetics
0:43
Example 1
0:44
Example 2
6:53
Example 3
8:58
Example 4
11:36
Example 5
16:36
Example 6: Part A
21:00
Example 6: Part B
25:09
Section 6: Equilibrium
Equilibrium, Part 1

46m

Intro
0:00
Equilibrium
1:32
Introduction to Equilibrium
1:33
Equilibrium Rules
14:00
Example 1: Part A
16:46
Example 1: Part B
18:48
Example 1: Part C
22:13
Example 1: Part D
24:55
Example 2: Part A
27:46
Example 2: Part B
31:22
Example 2: Part C
33:00
Reverse a Reaction
36:04
Example 3
37:24
Equilibrium, Part 2

40m 53s

Intro
0:00
Equilibrium
1:31
Equilibriums Involving Gases
1:32
General Equation
10:11
Example 1: Question
11:55
Example 1: Answer
13:43
Example 2: Question
19:08
Example 2: Answer
21:37
Example 3: Question
33:40
Example 3: Answer
35:24
Equilibrium: Reaction Quotient

45m 53s

Intro
0:00
Equilibrium
0:57
Reaction Quotient
0:58
If Q > K
5:37
If Q < K
6:52
If Q = K
7:45
Example 1: Part A
8:24
Example 1: Part B
13:11
Example 2: Question
20:04
Example 2: Answer
22:15
Example 3: Question
30:54
Example 3: Answer
32:52
Steps in Solving Equilibrium Problems
42:40
Equilibrium: Examples

31m 51s

Intro
0:00
Equilibrium
1:09
Example 1: Question
1:10
Example 1: Answer
4:15
Example 2: Question
13:04
Example 2: Answer
15:20
Example 3: Question
25:03
Example 3: Answer
26:32
Le Chatelier's principle & Equilibrium

40m 52s

Intro
0:00
Le Chatelier
1:05
Le Chatelier Principle
1:06
Concentration: Add 'x'
5:25
Concentration: Subtract 'x'
7:50
Example 1
9:44
Change in Pressure
12:53
Example 2
20:40
Temperature: Exothermic and Endothermic
24:33
Example 3
29:55
Example 4
35:30
Section 7: Acids & Bases
Acids and Bases

50m 11s

Intro
0:00
Acids and Bases
1:14
Bronsted-Lowry Acid-Base Model
1:28
Reaction of an Acid with Water
4:36
Acid Dissociation
10:51
Acid Strength
13:48
Example 1
21:22
Water as an Acid & a Base
25:25
Example 2: Part A
32:30
Example 2: Part B
34:47
Example 3: Part A
35:58
Example 3: Part B
39:33
pH Scale
41:12
Example 4
43:56
pH of Weak Acid Solutions

43m 52s

Intro
0:00
pH of Weak Acid Solutions
1:12
pH of Weak Acid Solutions
1:13
Example 1
6:26
Example 2
14:25
Example 3
24:23
Example 4
30:38
Percent Dissociation: Strong & Weak Bases

43m 4s

Intro
0:00
Bases
0:33
Percent Dissociation: Strong & Weak Bases
0:45
Example 1
6:23
Strong Base Dissociation
11:24
Example 2
13:02
Weak Acid and General Reaction
17:38
Example: NaOH → Na⁺ + OH⁻
20:30
Strong Base and Weak Base
23:49
Example 4
24:54
Example 5
33:51
Polyprotic Acids

35m 34s

Intro
0:00
Polyprotic Acids
1:04
Acids Dissociation
1:05
Example 1
4:51
Example 2
17:30
Example 3
31:11
Salts and Their Acid-Base Properties

41m 14s

Intro
0:00
Salts and Their Acid-Base Properties
0:11
Salts and Their Acid-Base Properties
0:15
Example 1
7:58
Example 2
14:00
Metal Ion and Acidic Solution
22:00
Example 3
28:35
NH₄F → NH₄⁺ + F⁻
34:05
Example 4
38:03
Common Ion Effect & Buffers

41m 58s

Intro
0:00
Common Ion Effect & Buffers
1:16
Covalent Oxides Produce Acidic Solutions in Water
1:36
Ionic Oxides Produce Basic Solutions in Water
4:15
Practice Example 1
6:10
Practice Example 2
9:00
Definition
12:27
Example 1: Part A
16:49
Example 1: Part B
19:54
Buffer Solution
25:10
Example of Some Buffers: HF and NaF
30:02
Example of Some Buffers: Acetic Acid & Potassium Acetate
31:34
Example of Some Buffers: CH₃NH₂ & CH₃NH₃Cl
33:54
Example 2: Buffer Solution
36:36
Buffer

32m 24s

Intro
0:00
Buffers
1:20
Buffer Solution
1:21
Adding Base
5:03
Adding Acid
7:14
Example 1: Question
9:48
Example 1: Recall
12:08
Example 1: Major Species Upon Addition of NaOH
16:10
Example 1: Equilibrium, ICE Chart, and Final Calculation
24:33
Example 1: Comparison
29:19
Buffers, Part II

40m 6s

Intro
0:00
Buffers
1:27
Example 1: Question
1:32
Example 1: ICE Chart
3:15
Example 1: Major Species Upon Addition of OH⁻, But Before Rxn
7:23
Example 1: Equilibrium, ICE Chart, and Final Calculation
12:51
Summary
17:21
Another Look at Buffering & the Henderson-Hasselbalch equation
19:00
Example 2
27:08
Example 3
32:01
Buffers, Part III

38m 43s

Intro
0:00
Buffers
0:25
Buffer Capacity Part 1
0:26
Example 1
4:10
Buffer Capacity Part 2
19:29
Example 2
25:12
Example 3
32:02
Titrations: Strong Acid and Strong Base

42m 42s

Intro
0:00
Titrations: Strong Acid and Strong Base
1:11
Definition of Titration
1:12
Sample Problem
3:33
Definition of Titration Curve or pH Curve
9:46
Scenario 1: Strong Acid- Strong Base Titration
11:00
Question
11:01
Part 1: No NaOH is Added
14:00
Part 2: 10.0 mL of NaOH is Added
15:50
Part 3: Another 10.0 mL of NaOH & 20.0 mL of NaOH are Added
22:19
Part 4: 50.0 mL of NaOH is Added
26:46
Part 5: 100.0 mL (Total) of NaOH is Added
27:26
Part 6: 150.0 mL (Total) of NaOH is Added
32:06
Part 7: 200.0 mL of NaOH is Added
35:07
Titrations Curve for Strong Acid and Strong Base
35:43
Titrations: Weak Acid and Strong Base

42m 3s

Intro
0:00
Titrations: Weak Acid and Strong Base
0:43
Question
0:44
Part 1: No NaOH is Added
1:54
Part 2: 10.0 mL of NaOH is Added
5:17
Part 3: 25.0 mL of NaOH is Added
14:01
Part 4: 40.0 mL of NaOH is Added
21:55
Part 5: 50.0 mL (Total) of NaOH is Added
22:25
Part 6: 60.0 mL (Total) of NaOH is Added
31:36
Part 7: 75.0 mL (Total) of NaOH is Added
35:44
Titration Curve
36:09
Titration Examples & Acid-Base Indicators

52m 3s

Intro
0:00
Examples and Indicators
0:25
Example 1: Question
0:26
Example 1: Solution
2:03
Example 2: Question
12:33
Example 2: Solution
14:52
Example 3: Question
23:45
Example 3: Solution
25:09
Acid/Base Indicator Overview
34:45
Acid/Base Indicator Example
37:40
Acid/Base Indicator General Result
47:11
Choosing Acid/Base Indicator
49:12
Section 8: Solubility
Solubility Equilibria

36m 25s

Intro
0:00
Solubility Equilibria
0:48
Solubility Equilibria Overview
0:49
Solubility Product Constant
4:24
Definition of Solubility
9:10
Definition of Solubility Product
11:28
Example 1
14:09
Example 2
20:19
Example 3
27:30
Relative Solubilities
31:04
Solubility Equilibria, Part II

42m 6s

Intro
0:00
Solubility Equilibria
0:46
Common Ion Effect
0:47
Example 1
3:14
pH & Solubility
13:00
Example of pH & Solubility
15:25
Example 2
23:06
Precipitation & Definition of the Ion Product
26:48
If Q > Ksp
29:31
If Q < Ksp
30:27
Example 3
32:58
Solubility Equilibria, Part III

43m 9s

Intro
0:00
Solubility Equilibria
0:55
Example 1: Question
0:56
Example 1: Step 1 - Check to See if Anything Precipitates
2:52
Example 1: Step 2 - Stoichiometry
10:47
Example 1: Step 3 - Equilibrium
16:34
Example 2: Selective Precipitation (Question)
21:02
Example 2: Solution
23:41
Classical Qualitative Analysis
29:44
Groups: 1-5
38:44
Section 9: Complex Ions
Complex Ion Equilibria

43m 38s

Intro
0:00
Complex Ion Equilibria
0:32
Complex Ion
0:34
Ligan Examples
1:51
Ligand Definition
3:12
Coordination
6:28
Example 1
8:08
Example 2
19:13
Complex Ions & Solubility

31m 30s

Intro
0:00
Complex Ions and Solubility
0:23
Recall: Classical Qualitative Analysis
0:24
Example 1
6:10
Example 2
16:16
Dissolving a Water-Insoluble Ionic Compound: Method 1
23:38
Dissolving a Water-Insoluble Ionic Compound: Method 2
28:13
Section 10: Chemical Thermodynamics
Spontaneity, Entropy, & Free Energy, Part I

56m 28s

Intro
0:00
Spontaneity, Entropy, Free Energy
2:25
Energy Overview
2:26
Equation: ∆E = q + w
4:30
State Function/ State Property
8:35
Equation: w = -P∆V
12:00
Enthalpy: H = E + PV
14:50
Enthalpy is a State Property
17:33
Exothermic and Endothermic Reactions
19:20
First Law of Thermodynamic
22:28
Entropy
25:48
Spontaneous Process
33:53
Second Law of Thermodynamic
36:51
More on Entropy
42:23
Example
43:55
Spontaneity, Entropy, & Free Energy, Part II

39m 55s

Intro
0:00
Spontaneity, Entropy, Free Energy
1:30
∆S of Universe = ∆S of System + ∆S of Surrounding
1:31
Convention
3:32
Examining a System
5:36
Thermodynamic Property: Sign of ∆S
16:52
Thermodynamic Property: Magnitude of ∆S
18:45
Deriving Equation: ∆S of Surrounding = -∆H / T
20:25
Example 1
25:51
Free Energy Equations
29:22
Spontaneity, Entropy, & Free Energy, Part III

30m 10s

Intro
0:00
Spontaneity, Entropy, Free Energy
0:11
Example 1
2:38
Key Concept of Example 1
14:06
Example 2
15:56
Units for ∆H, ∆G, and S
20:56
∆S of Surrounding & ∆S of System
22:00
Reaction Example
24:17
Example 3
26:52
Spontaneity, Entropy, & Free Energy, Part IV

30m 7s

Intro
0:00
Spontaneity, Entropy, Free Energy
0:29
Standard Free Energy of Formation
0:58
Example 1
4:34
Reaction Under Non-standard Conditions
13:23
Example 2
16:26
∆G = Negative
22:12
∆G = 0
24:38
Diagram Example of ∆G
26:43
Spontaneity, Entropy, & Free Energy, Part V

44m 56s

Intro
0:00
Spontaneity, Entropy, Free Energy
0:56
Equations: ∆G of Reaction, ∆G°, and K
0:57
Example 1: Question
6:50
Example 1: Part A
9:49
Example 1: Part B
15:28
Example 2
17:33
Example 3
23:31
lnK = (- ∆H° ÷ R) ( 1 ÷ T) + ( ∆S° ÷ R)
31:36
Maximum Work
35:57
Section 11: Electrochemistry
Oxidation-Reduction & Balancing

39m 23s

Intro
0:00
Oxidation-Reduction and Balancing
2:06
Definition of Electrochemistry
2:07
Oxidation and Reduction Review
3:05
Example 1: Assigning Oxidation State
10:15
Example 2: Is the Following a Redox Reaction?
18:06
Example 3: Step 1 - Write the Oxidation & Reduction Half Reactions
22:46
Example 3: Step 2 - Balance the Reaction
26:44
Example 3: Step 3 - Multiply
30:11
Example 3: Step 4 - Add
32:07
Example 3: Step 5 - Check
33:29
Galvanic Cells

43m 9s

Intro
0:00
Galvanic Cells
0:39
Example 1: Balance the Following Under Basic Conditions
0:40
Example 1: Steps to Balance Reaction Under Basic Conditions
3:25
Example 1: Solution
5:23
Example 2: Balance the Following Reaction
13:56
Galvanic Cells
18:15
Example 3: Galvanic Cells
28:19
Example 4: Galvanic Cells
35:12
Cell Potential

48m 41s

Intro
0:00
Cell Potential
2:08
Definition of Cell Potential
2:17
Symbol and Unit
5:50
Standard Reduction Potential
10:16
Example Figure 1
13:08
Example Figure 2
19:00
All Reduction Potentials are Written as Reduction
23:10
Cell Potential: Important Fact 1
26:49
Cell Potential: Important Fact 2
27:32
Cell Potential: Important Fact 3
28:54
Cell Potential: Important Fact 4
30:05
Example Problem 1
32:29
Example Problem 2
38:38
Potential, Work, & Free Energy

41m 23s

Intro
0:00
Potential, Work, Free Energy
0:42
Descriptions of Galvanic Cell
0:43
Line Notation
5:33
Example 1
6:26
Example 2
11:15
Example 3
15:18
Equation: Volt
22:20
Equations: Cell Potential, Work, and Charge
28:30
Maximum Cell Potential is Related to the Free Energy of the Cell Reaction
35:09
Example 4
37:42
Cell Potential & Concentration

34m 19s

Intro
0:00
Cell Potential & Concentration
0:29
Example 1: Question
0:30
Example 1: Nernst Equation
4:43
Example 1: Solution
7:01
Cell Potential & Concentration
11:27
Example 2
16:38
Manipulating the Nernst Equation
25:15
Example 3
28:43
Electrolysis

33m 21s

Intro
0:00
Electrolysis
3:16
Electrolysis: Part 1
3:17
Electrolysis: Part 2
5:25
Galvanic Cell Example
7:13
Nickel Cadmium Battery
12:18
Ampere
16:00
Example 1
20:47
Example 2
25:47
Section 12: Light
Light

44m 45s

Intro
0:00
Light
2:14
Introduction to Light
2:15
Frequency, Speed, and Wavelength of Waves
3:58
Units and Equations
7:37
Electromagnetic Spectrum
12:13
Example 1: Calculate the Frequency
17:41
E = hν
21:30
Example 2: Increment of Energy
25:12
Photon Energy of Light
28:56
Wave and Particle
31:46
Example 3: Wavelength of an Electron
34:46
Section 13: Quantum Mechanics
Quantum Mechanics & Electron Orbitals

54m

Intro
0:00
Quantum Mechanics & Electron Orbitals
0:51
Quantum Mechanics & Electron Orbitals Overview
0:52
Electron Orbital and Energy Levels for the Hydrogen Atom
8:47
Example 1
13:41
Quantum Mechanics: Schrodinger Equation
19:19
Quantum Numbers Overview
31:10
Principal Quantum Numbers
33:28
Angular Momentum Numbers
34:55
Magnetic Quantum Numbers
36:35
Spin Quantum Numbers
37:46
Primary Level, Sublevels, and Sub-Sub-Levels
39:42
Example
42:17
Orbital & Quantum Numbers
49:32
Electron Configurations & Diagrams

34m 4s

Intro
0:00
Electron Configurations & Diagrams
1:08
Electronic Structure of Ground State Atom
1:09
Order of Electron Filling
3:50
Electron Configurations & Diagrams: H
8:41
Electron Configurations & Diagrams: He
9:12
Electron Configurations & Diagrams: Li
9:47
Electron Configurations & Diagrams: Be
11:17
Electron Configurations & Diagrams: B
12:05
Electron Configurations & Diagrams: C
13:03
Electron Configurations & Diagrams: N
14:55
Electron Configurations & Diagrams: O
15:24
Electron Configurations & Diagrams: F
16:25
Electron Configurations & Diagrams: Ne
17:00
Electron Configurations & Diagrams: S
18:08
Electron Configurations & Diagrams: Fe
20:08
Introduction to Valence Electrons
23:04
Valence Electrons of Oxygen
23:44
Valence Electrons of Iron
24:02
Valence Electrons of Arsenic
24:30
Valence Electrons: Exceptions
25:36
The Periodic Table
27:52
Section 14: Intermolecular Forces
Vapor Pressure & Changes of State

52m 43s

Intro
0:00
Vapor Pressure and Changes of State
2:26
Intermolecular Forces Overview
2:27
Hydrogen Bonding
5:23
Heat of Vaporization
9:58
Vapor Pressure: Definition and Example
11:04
Vapor Pressures is Mostly a Function of Intermolecular Forces
17:41
Vapor Pressure Increases with Temperature
20:52
Vapor Pressure vs. Temperature: Graph and Equation
22:55
Clausius-Clapeyron Equation
31:55
Example 1
32:13
Heating Curve
35:40
Heat of Fusion
41:31
Example 2
43:45
Phase Diagrams & Solutions

31m 17s

Intro
0:00
Phase Diagrams and Solutions
0:22
Definition of a Phase Diagram
0:50
Phase Diagram Part 1: H₂O
1:54
Phase Diagram Part 2: CO₂
9:59
Solutions: Solute & Solvent
16:12
Ways of Discussing Solution Composition: Mass Percent or Weight Percent
18:46
Ways of Discussing Solution Composition: Molarity
20:07
Ways of Discussing Solution Composition: Mole Fraction
20:48
Ways of Discussing Solution Composition: Molality
21:41
Example 1: Question
22:06
Example 1: Mass Percent
24:32
Example 1: Molarity
25:53
Example 1: Mole Fraction
28:09
Example 1: Molality
29:36
Vapor Pressure of Solutions

37m 23s

Intro
0:00
Vapor Pressure of Solutions
2:07
Vapor Pressure & Raoult's Law
2:08
Example 1
5:21
When Ionic Compounds Dissolve
10:51
Example 2
12:38
Non-Ideal Solutions
17:42
Negative Deviation
24:23
Positive Deviation
29:19
Example 3
31:40
Colligatives Properties

34m 11s

Intro
0:00
Colligative Properties
1:07
Boiling Point Elevation
1:08
Example 1: Question
5:19
Example 1: Solution
6:52
Freezing Point Depression
12:01
Example 2: Question
14:46
Example 2: Solution
16:34
Osmotic Pressure
20:20
Example 3: Question
28:00
Example 3: Solution
30:16
Section 15: Bonding
Bonding & Lewis Structure

48m 39s

Intro
0:00
Bonding & Lewis Structure
2:23
Covalent Bond
2:24
Single Bond, Double Bond, and Triple Bond
4:11
Bond Length & Intermolecular Distance
5:51
Definition of Electronegativity
8:42
Bond Polarity
11:48
Bond Energy
20:04
Example 1
24:31
Definition of Lewis Structure
31:54
Steps in Forming a Lewis Structure
33:26
Lewis Structure Example: H₂
36:53
Lewis Structure Example: CH₄
37:33
Lewis Structure Example: NO⁺
38:43
Lewis Structure Example: PCl₅
41:12
Lewis Structure Example: ICl₄⁻
43:05
Lewis Structure Example: BeCl₂
45:07
Resonance & Formal Charge

36m 59s

Intro
0:00
Resonance and Formal Charge
0:09
Resonance Structures of NO₃⁻
0:25
Resonance Structures of NO₂⁻
12:28
Resonance Structures of HCO₂⁻
16:28
Formal Charge
19:40
Formal Charge Example: SO₄²⁻
21:32
Formal Charge Example: CO₂
31:33
Formal Charge Example: HCN
32:44
Formal Charge Example: CN⁻
33:34
Formal Charge Example: 0₃
34:43
Shapes of Molecules

41m 21s

Intro
0:00
Shapes of Molecules
0:35
VSEPR
0:36
Steps in Determining Shapes of Molecules
6:18
Linear
11:38
Trigonal Planar
11:55
Tetrahedral
12:45
Trigonal Bipyramidal
13:23
Octahedral
14:29
Table: Shapes of Molecules
15:40
Example: CO₂
21:11
Example: NO₃⁻
24:01
Example: H₂O
27:00
Example: NH₃
29:48
Example: PCl₃⁻
32:18
Example: IF₄⁺
34:38
Example: KrF₄
37:57
Hybrid Orbitals

40m 17s

Intro
0:00
Hybrid Orbitals
0:13
Introduction to Hybrid Orbitals
0:14
Electron Orbitals for CH₄
5:02
sp³ Hybridization
10:52
Example: sp³ Hybridization
12:06
sp² Hybridization
14:21
Example: sp² Hybridization
16:11
σ Bond
19:10
π Bond
20:07
sp Hybridization & Example
22:00
dsp³ Hybridization & Example
27:36
d²sp³ Hybridization & Example
30:36
Example: Predict the Hybridization and Describe the Molecular Geometry of CO
32:31
Example: Predict the Hybridization and Describe the Molecular Geometry of BF₄⁻
35:17
Example: Predict the Hybridization and Describe the Molecular Geometry of XeF₂
37:09
Section 16: AP Practice Exam
AP Practice Exam: Multiple Choice, Part I

52m 34s

Intro
0:00
Multiple Choice
1:21
Multiple Choice 1
1:22
Multiple Choice 2
2:23
Multiple Choice 3
3:38
Multiple Choice 4
4:34
Multiple Choice 5
5:16
Multiple Choice 6
5:41
Multiple Choice 7
6:20
Multiple Choice 8
7:03
Multiple Choice 9
7:31
Multiple Choice 10
9:03
Multiple Choice 11
11:52
Multiple Choice 12
13:16
Multiple Choice 13
13:56
Multiple Choice 14
14:52
Multiple Choice 15
15:43
Multiple Choice 16
16:20
Multiple Choice 17
16:55
Multiple Choice 18
17:22
Multiple Choice 19
18:59
Multiple Choice 20
20:24
Multiple Choice 21
22:20
Multiple Choice 22
23:29
Multiple Choice 23
24:30
Multiple Choice 24
25:24
Multiple Choice 25
26:21
Multiple Choice 26
29:06
Multiple Choice 27
30:42
Multiple Choice 28
33:28
Multiple Choice 29
34:38
Multiple Choice 30
35:37
Multiple Choice 31
37:31
Multiple Choice 32
38:28
Multiple Choice 33
39:50
Multiple Choice 34
42:57
Multiple Choice 35
44:18
Multiple Choice 36
45:52
Multiple Choice 37
48:02
Multiple Choice 38
49:25
Multiple Choice 39
49:43
Multiple Choice 40
50:16
Multiple Choice 41
50:49
AP Practice Exam: Multiple Choice, Part II

32m 15s

Intro
0:00
Multiple Choice
0:12
Multiple Choice 42
0:13
Multiple Choice 43
0:33
Multiple Choice 44
1:16
Multiple Choice 45
2:36
Multiple Choice 46
5:22
Multiple Choice 47
6:35
Multiple Choice 48
8:02
Multiple Choice 49
10:05
Multiple Choice 50
10:26
Multiple Choice 51
11:07
Multiple Choice 52
12:01
Multiple Choice 53
12:55
Multiple Choice 54
16:12
Multiple Choice 55
18:11
Multiple Choice 56
19:45
Multiple Choice 57
20:15
Multiple Choice 58
23:28
Multiple Choice 59
24:27
Multiple Choice 60
26:45
Multiple Choice 61
29:15
AP Practice Exam: Multiple Choice, Part III

32m 50s

Intro
0:00
Multiple Choice
0:16
Multiple Choice 62
0:17
Multiple Choice 63
1:57
Multiple Choice 64
6:16
Multiple Choice 65
8:05
Multiple Choice 66
9:18
Multiple Choice 67
10:38
Multiple Choice 68
12:51
Multiple Choice 69
14:32
Multiple Choice 70
17:35
Multiple Choice 71
22:44
Multiple Choice 72
24:27
Multiple Choice 73
27:46
Multiple Choice 74
29:39
Multiple Choice 75
30:23
AP Practice Exam: Free response Part I

47m 22s

Intro
0:00
Free Response
0:15
Free Response 1: Part A
0:16
Free Response 1: Part B
4:15
Free Response 1: Part C
5:47
Free Response 1: Part D
9:20
Free Response 1: Part E. i
10:58
Free Response 1: Part E. ii
16:45
Free Response 1: Part E. iii
26:03
Free Response 2: Part A. i
31:01
Free Response 2: Part A. ii
33:38
Free Response 2: Part A. iii
35:20
Free Response 2: Part B. i
37:38
Free Response 2: Part B. ii
39:30
Free Response 2: Part B. iii
44:44
AP Practice Exam: Free Response Part II

43m 5s

Intro
0:00
Free Response
0:12
Free Response 3: Part A
0:13
Free Response 3: Part B
6:25
Free Response 3: Part C. i
11:33
Free Response 3: Part C. ii
12:02
Free Response 3: Part D
14:30
Free Response 4: Part A
21:03
Free Response 4: Part B
22:59
Free Response 4: Part C
24:33
Free Response 4: Part D
27:22
Free Response 4: Part E
28:43
Free Response 4: Part F
29:35
Free Response 4: Part G
30:15
Free Response 4: Part H
30:48
Free Response 5: Diagram
32:00
Free Response 5: Part A
34:14
Free Response 5: Part B
36:07
Free Response 5: Part C
37:45
Free Response 5: Part D
39:00
Free Response 5: Part E
40:26
AP Practice Exam: Free Response Part III

28m 36s

Intro
0:00
Free Response
0:43
Free Response 6: Part A. i
0:44
Free Response 6: Part A. ii
3:08
Free Response 6: Part A. iii
5:02
Free Response 6: Part B. i
7:11
Free Response 6: Part B. ii
9:40
Free Response 7: Part A
11:14
Free Response 7: Part B
13:45
Free Response 7: Part C
15:43
Free Response 7: Part D
16:54
Free Response 8: Part A. i
19:15
Free Response 8: Part A. ii
21:16
Free Response 8: Part B. i
23:51
Free Response 8: Part B. ii
25:07
Loading...
This is a quick preview of the lesson. For full access, please Log In or Sign up.
For more information, please see full course syllabus of AP Chemistry
Bookmark & Share Embed

Share this knowledge with your friends!

Copy & Paste this embed code into your website’s HTML

Please ensure that your website editor is in text mode when you paste the code.
(In Wordpress, the mode button is on the top right corner.)
  ×
  • - Allow users to view the embedded video in full-size.
Since this lesson is not free, only the preview will appear on your website.
  • Discussion

  • Answer Engine

  • Study Guides

  • Download Lecture Slides

  • Table of Contents

  • Transcription

  • Related Books & Services

Lecture Comments (2)

1 answer

Last reply by: Professor Hovasapian
Tue Aug 14, 2012 7:41 PM

Post by Justin Jones Jones on August 14, 2012

Is line notation the same thing as cell notation?

Potential, Work, & Free Energy

Lecture Slides are screen-captured images of important points in the lecture. Students can download and print out these lecture slide images to do practice problems as well as take notes while watching the lecture.

  • Intro 0:00
  • Potential, Work, Free Energy 0:42
    • Descriptions of Galvanic Cell
    • Line Notation
    • Example 1
    • Example 2
    • Example 3
    • Equation: Volt
    • Equations: Cell Potential, Work, and Charge
    • Maximum Cell Potential is Related to the Free Energy of the Cell Reaction
    • Example 4

Transcription: Potential, Work, & Free Energy

Hello, and welcome back to Educator.com, and welcome back to AP Chemistry.0000

Today, we are going to continue our discussion of electrochemistry, and we are going to talk about cell potential, work, and free energy--the relation between the potential, the work, and the free energy.0004

Before I actually get into that, though, I would like to spend a little bit of time talking about something called line notation.0014

It is a shorthand notation that actually describes a galvanic cell--a voltaic cell.0021

Let's go ahead and take a look at that first, and make sure we have a nice, complete description of this cell, so we are solid with that; and then we will continue on and discuss the relationship between thermodynamics and the electrochemistry.0027

OK, here we go.0041

A complete description of a galvanic cell includes these things...so a complete description of a galvanic cell (also called voltaic cell) contains three things.0044

You will see this list...sometimes it's listed as 4; sometimes it's listed as 5; it depends on how many things you actually want to put together and separate and be specific.0071

I tend to think of it as three things, and you will see why in a minute.0078

OK, so the first thing that it needs is the cell potential; so we have to know what the cell potential is, and that cell potential comes from, remember, the oxidation and reduction reactions, arranged and balanced and added--that is what gives you the cell potential.0082

The individual potentials are called the standard reduction potentials for the individual components.0099

OK, so the cell potential, and balanced equation: so we need a balanced equation, also.0105

And again, that comes from adding the two half-reactions--the reduction half-reaction and the oxidation reaction.0111

OK, #2: We need to know the direction of electron flow (in other words, the designation of what is the anode and what is the cathode).0118

Direction of electron flow...when the circuit is open: OK, so we measure a potential--that doesn't mean we have opened the circuit; we have measured the pressure (that is the pull or the push on the electrons) once we actually open that circuit and allow the electrons to flow.0126

Potential is a measure of that pressure; current means the actual flow of electrons--we will talk more about current when we actually open the circuit in a little bit.0147

The direction of electron flow, which is a designation of anode and cathode...0157

And, as a quick reminder, electrons always flow from the anode to the cathode, because "anode" is where oxidation takes place...so anode to cathode...electron flow.0172

Oxidation takes place at the anode; reduction takes place at the cathode.0190

They both start with vowels; they both start with consonants--that is how I remember it.0197

OK, and 3 (which is probably the most important thing, from a practical point of view): We need the physical nature of each electrode, of each compartment.0202

So, the physical nature--in other words, what makes it up--what components are we using? Are they ions? Are they solids? What is an ion--what is a solid?--things like that--so, the physical nature of each electrode and the ions present in each compartment.0212

Now, when we say "ions," we are talking about the ions that are involved in the oxidation-reduction; we are not talking about the counter-ions.0246

OK--like, for example, if we are dealing with zinc and copper, we put a solution; we put the zinc metal in; one of the compartments is going to contain zinc sulfate; let's say the other contains copper sulfate--we are only concerned with the zinc and copper, because those are the ones that are going to transform.0252

The sulfate is just a spectator ion--it's not going to do anything; those don't matter.0266

OK, and if none of the substances participating in the reaction is a conducting solid, then an inert material (more often than not, it's going to be platinum) must act as the electrode.0272

So, if one of the things involved is not a conducting metal (like zinc--a conducting metal--you can use that as the electrode)--if not--then you will have to use platinum.0325

OK, so let me give the definition of line notation.0333

Line notation is a shorthand for describing an electrochemical cell (in other words, a galvanic or voltaic cell).0340

There is another type of cell called electrolytic, which we will actually talk about next time...actually, not next time--not next lesson, but the lesson after that.0373

That is also considered electrochemical: "electrochemical" is just your general term for it.0381

OK, so let's do an example.0386

Let's go ahead and...you know what, let me--that's fine; I'll do it over here.0389

Example #1: For the reaction that we saw before (the reaction which was 2 aluminum ion, plus 3 magnesium ion, becomes 2 pieces of aluminum metal--by 2 pieces, I mean 2 moles or 2 atoms--plus 3 magnesium ion)--in this case, the aluminum is going to reduce; the magnesium is going to oxidize; and here is what the shorthand notation looks like.0397

It's going to be Mg, single line, Mg2+ (oops, let's make this a little more clear), double line, Al3+, single line, Al.0430

So, Mg on the left; Mg2+ next to it; double line; Al3+ and Al; so now, let's talk about what these things mean.0448

Let me actually write it over again: Mg, Mg2+, a line, Al3+, Al; and it's OK if the lines are slanted; it's not a problem--they don't have to be vertical.0457

OK, here is what is going on: the anode is on the left--is at the left, with the electrode (the actual electrode--the physical metal piece) at the far left.0475

So, this is the anode: it's on the left-hand side; we are demonstrating electron flow from left to right--that is the whole idea: electrons move that way.0500

Anode...and the actual electrode itself, the magnesium metal, is going to be on the far left.0512

The cathode is on the right, with the electrode itself on the far right.0519

Aluminum is the electrode; this aluminum-aluminum ion combination is considered the cathode; this metal--the electrode itself (the physical electrode)--that is on the far right.0537

OK, now, phase boundary: phase boundary is a single line.0550

A phase boundary means--well, we have three phases: solid, liquid, and gas; in this case, the phase boundary is going to be between solid and aqueous, aqueous and solid.0557

Magnesium metal is sitting in a solution that contains magnesium ion; so there is magnesium ion that is in one phase (it's aqueous), and here it's magnesium solid.0566

If you want, you can go ahead and put "aqueous," if you want to be absolutely--make sure that everything is there.0578

You put Mg; you can put a little s subscript for solid; you can put aq; but that is what this means any time you see an ion, unless you are specifically talking about a gas phase ion (which, for most chemistry, you don't).0583

I think the only people that actually deal with gas-phase ions are going to be physical chemists, and since we are not doing high-end physical chemistry here, it's not a problem.0596

We know we are talking about an aqueous solution--we know we are talking about a galvanic cell, a wet cell.0604

OK, so the phase boundary is a single line (sorry about that--it might be nice if I actually finish what I'm writing before I get into a discussion of it)--so this single line here--it's a phase boundary between Mg and Mg+, aluminum solution and solid aluminum metal.0610

Now, the compartments are separated by a double line; so you see the double line right there; OK.0628

This double line represents the porous disk, the one that allows counter-ion flow; it represents the porous disk or the salt bridge, depending on what the physical arrangement is.0652

And again, nowadays, a porous disk is what we use most of the time.0670

OK, so let's take a look at another example, Example #2.0675

Now, for the reaction (slightly more complicated reaction--this is the permanganate and chlorate--so let's do): 2 MnO4- + 6 H+ + 5 ClO3- goes to 2 Mn2+ + 3 H2O + 5 ClO4-...0680

So, this says that, when you mix permanganate and chlorate in a solution, the permanganate (or the manganese in the permanganate) is going to reduce to manganese 2+; the chlorine is going to oxidize to chlorine 7+ (it's going to go from 5+ to 7+).0711

So, this looks like...so we know that the anode is going to be the chlorate-perchlorate solution, and the anode is going to have the permanganate and manganese solution.0730

Well, neither one of those is actually a conducting metal; so we are going to have to use an inert electrode; so it looks like this.0744

So we write: Pt, single line (that is a solid), and then we write ClO3-, ClO4-.0751

Now notice: I went from left to right; I didn't write ClO4, ClO3; again, we are talking about the direction of...as we go from left to right, what turns into what.0761

So, in this case, ClO3 is going to turn into ClO4; if you are not exactly sure what, just look up here: ClO3 comes first; ClO4 is next; so this is on the left; this is on the right.0773

That is the anode; the cathode compartment...the MnO4 becomes Mn2+, so this is written MnO4-, Mn2+.0783

Notice: I didn't include...0794

Oh, I need to finish it off with a platinum electrode; again, none of these is a...these are all aqueous solutions: aqueous ion, aqueous ion...none of these is a conducting metal, which is why I have to use the platinum electrode.0796

This is the line notation for the cell that is based on this reaction.0809

That is what we are doing: this gives us a notation for the actual physical arrangement of the cell that is based on (a galvanic cell that is founded on) this reaction.0815

Now, notice: I didn't do anything about the H2O, and I didn't do anything about the H+.0825

They are just there; they are not actually...I don't want to say they are not involved in the process--they actually make the process happen; yes, they are involved, but they are not directly involved.0831

What is being oxidized is the chlorine, going from chlorine +5 to chlorine +7; here, the manganese is going from manganese +7 to manganese 2.0840

It is only the species that are involved in the oxidation-reduction that we are concerned with.0849

But, we do need the actual reaction itself.0853

OK, and again, if somebody didn't give us the reaction--if they just gave us this line notation--it is not a problem; we can recover the equation--it's very, very easy.0857

You just take a look at a table of standard reduction potentials (the ones that have the list from positive to negative or negative to positive--different books actually put them in different orders).0865

We look up the ClO3 to ClO4; we write that half-reaction with its reduction potential.0876

We look up the MnO4-, Mn2+ reaction--that is in there, and again, it is all written as a reduction--with its electric potential.0882

We decide which one is higher; the one that is higher stays as written; the one that is lower--we flip it, and that becomes the oxidation reaction.0890

We balance it (remember, H's, H2O's, electrons, everything; cancel; add everything; add this)...well, that is where this comes from.0898

We can go from equation to line notation; we can go from line notation to equation--not a problem.0908

These things are what is important, what is involved in there.0913

OK, so let's go ahead and do one more example here.0917

Example 3: Give a complete description of a cell based on the following reaction...oh, I'm sorry; not based on the following reaction--that is what we are doing; based on the following substances.0925

So here, they are not telling us anything; they are just giving us a couple of substances to work with; we have to do everything--which is nice; we get a nice chance to see the whole process.0957

Cl2, Cl-, and Br2, Br-: so we want to construct a cell that uses these components.0967

Well, OK: let's see: let's see what is going on.0978

The first thing we want to do is check the table of standard reduction potentials.0982

I'll say "consult" (how is that?): we want to consult a table of standard reduction potentials; and remember, they are all written as reductions--that is why is called a standard reduction potential (a table of standard reduction potentials).0991

Here is what we find: when we look at the Br2, Br- combination, we get the following: Br2 + 2 electrons goes to 2 Br-.1011

It tells me that the standard reduction potential for that equals 1.09 volts.1027

If I check the chlorine-chloride combination in the table (I just run down the table until I find what I am looking for), it tells me that chlorine, plus 2 electrons, becomes 2 chloride ions, and the standard reduction potential for that is 1.36 volts.1033

Well, which one is higher? 1.36 volts is higher.1052

So, that stays as written: that is the reduction reaction.1055

That means this one has to be flipped; when we flip it, that becomes the oxidation reaction: 2 Br- goes to Br2 + 2 electrons.1060

Because we flipped it, the standard reduction potential changes and becomes negative.1079

OK, well, now that we have a reduction reaction and we have an oxidation reaction, we know that chlorine is going to be the one that is going to be reduced.1086

Bromide is going to end up oxidizing to bromine.1095

Well, everything balances; there are no oxygens, no hydrogens; now, we just need to make sure that the electrons balance to cancel.1101

We have 2 electrons on the left, 2 electrons on the right; everything is good--we don't have to do anything; we can just add straight.1109

If not, then we would have to go through that process of balancing the reduction half-reaction, balancing the oxidation half-reaction, adding the reactions (remember that process?)...1116

That cancels that, and my overall reaction is going to be the following--I have: chlorine, plus 2 bromides, is going to be converted into 2 chlorides, plus bromine.1126

The cell potential is going to be the sum of those two, 1.36-1.09; and I end up with...it looks like it's going to be 0.27.1138

And again, I hope you check my arithmetic; I'm notorious, notorious, for not being able to do arithmetic.1160

OK, so here we go: that is the first part--remember, we said "a complete description."1165

We have our balanced reaction, and we have our cell potential; so we are good--that is the first part.1170

Now, we want to designate the anode: the anode is where oxidation takes place.1176

What is going to be oxidized is: the bromide goes to bromine (right?--oxidation: bromide goes to bromine--so that is going to be the Br-).1183

The cathode (yes, we can write this; that is not a problem: Br to Br2) is where reduction takes place, and the reduction reaction is: Cl2 to Cl-.1193

So, electron flow is that way.1212

Again, pictures are perfectly fine--pictures, I think, are actually better.1218

OK, now--the last thing we need is, of course, the physical description: we need the line notation: what does this look like?1222

Well, OK: bromine and chlorine are not conducting metals, and certainly bromide and chloride are just aqueous ions; so we are going to need an inert material.1228

We are going to use platinum, so: platinum; I'll put a single line here; the thing that is going to be oxidized--remember, the anode is on the left, where oxidation takes place, so that is going to be here.1241

It is going to be Br- becoming Br2; remember, we are going from the thing that is becoming (I'm doing it from your perspective); the thing that is becoming, that is turning into, goes to the right; so we are moving to the right.1254

Bromide becomes bromine, and then we have a double line (let me make that double line a little bit better), and then here, chlorine is becoming chloride; so here, Cl2, Cl-, single line, and then another platinum electrode.1272

That is the line notation.1291

This is a complete description, based on just substances that they give us; they just threw it out: they said, "Make me a galvanic cell based on chlorine and bromine."1293

Look through the standard reduction potentials; find the equations; pick which one is higher; that stays reduction; the other one--we have to flip it, because that is going to be oxidized.1303

We balance each one (in this case, they are already balanced); we add the potentials for a cell potential; we designate the anode; we designate the cathode; and then, we write the physical description as the line notation.1312

Standard, standard, standard; OK.1324

Now, we can start our discussion of cell potential, free energy, work...things like that.1328

Now, we are going to start discussing the connection between potential and thermodynamics.1334

All right, now let's see: let us reintroduce this volt--we have been talking about cell potential being volts, and we said that it is Joules per coulomb.1340

Well, so J/C; that is equivalent to V; well, let's think about what this means.1359

We know what a Joule is: a Joule is a unit of work--a Joule is a unit of energy.1365

A coulomb is a unit of charge; so, a coulomb doesn't mean 1 positive or 1 negative charge; those are just specific charges that we use to designate.1370

A coulomb is actually a unit of charge, but it isn't 1; it isn't + and -.1385

I'll explain what that means in just a minute.1392

Let me just talk about what this actually means--what is a volt?--what is a Joule per coulomb?1395

Well, here is what it means: for a 1-volt cell (so let's say we have some galvanic cell, and we measure the potential, and it turns out to be 1 volt), that is equivalent to 1 Joule per coulomb.1401

OK, this means: as 1 coulomb of charge flows through the wire, 1 Joule of work is done by the cell.1420

So, remember what we said: we said that, if we put two substances together that differ in a reduction potential, when we add them together, the cell potential that we get is a measure of a spontaneous reaction.1456

In other words, if we opened up that circuit and allowed the electrons to flow, they will flow naturally, spontaneously, without us doing anything.1470

Well, the flow of electron through a wire allows us to do work--basically, everything that you enjoy in your life is a flow of electrons (electricity).1476

A potential of 1 volt means that, for every coulomb of charge that passes through the wire (and I'll tell you what a coulomb is in just a minute, in terms of actual number of electrons)--as that much charge passes through the wire, 1 Joule of work is done.1486

So, if I have a 2-volt potential, that means, for every coulomb of charge (it's 2 Joules per coulomb) that passes through the wire, that cell can give you 2 Joules of work.1508

If I have a 15-volt cell...a 12-volt battery: a 12-volt battery means that, for every coulomb of charge that passes from the battery through whatever it is that you are running (like, for example, your starter engine on your car)--12 volts--that means it does 12 Joules of work on that whatever-it-is (on the starter).1520

That is the whole idea: so that is what a volt means--it is the amount of energy that the cell does every time 1 coulomb of charge is transferred.1543

I'll define what a coulomb means in just a minute; don't worry.1554

OK, and I should also say: this is the maximum work--the maximum amount of energy you can extract from a 1-volt cell.1557

"Maximum" means--well, in thermodynamics, you remember what "maximum" means; "maximum" means that is sort of an ideal; we never reach that ideal, and the reason we don't reach that ideal is because some of that work is actually dissipated as heat.1590

The reason it is dissipated as heat is because the second law of thermodynamics tells us that the entropy of the universe always has to increase in any spontaneous process.1606

Let me say that again--it's profoundly important: In any spontaneous process (which this is), the entropy of the universe has to increase.1615

Well, in order for the entropy of the universe to have to increase, we can't extract the maximum work available from a process.1627

Back in thermodynamics, we said that, let's say, we have a free energy difference of -50 Joules; well, that means -50 Joules is free energy that I can use to do work.1635

Unfortunately, if I am lucky, I get maybe 60% of that; all of the other 40% of those 50 Joules--they end up being dissipated as heat.1645

That is necessary, because it is a fundamental law of nature that the entropy of the universe has to increase for any spontaneous process.1656

This is why there is no such thing as a perpetual motion machine; a perpetual motion machine means that you get back what you put in; it will never happen that way.1665

You are always going to lose something as heat; so every cycle that you pass in a perpetual motion machine, you are going to be increasing the entropy of the universe; you are going to be losing heat; you are going to get less energy back, less energy back; at some point, the machine will just stop.1672

It is OK, theoretically; we can talk about the potential, and we can talk about the maximum work available, as long as you remember: the maximum work that you get won't be that.1686

So, for a 1-volt cell--yes, theoretically, you should be able to get 1 Joule for every coulomb; you are probably not going to get 1 Joule.1697

You will be lucky if you get about .5 or .6 Joules, and I do mean lucky.1704

That is all this means; OK.1708

Now, let us actually talk about cell potential and what this means in terms of cell potential.1712

Cell potential is equal to...well, as we said, it's equal to a Joule per coulomb.1721

Well, a Joule is a unit of work, and a coulomb is a unit of charge; so a Joule is a unit of work, and a coulomb is a unit of charge.1727

Well, work is W; charge is q; this is not the same q as heat; remember, this is different: when we are talking about electricity, q means charge.1742

And because the cell is actually doing work on the surroundings, that means the cell is doing work, so we are always looking at work from the system's point of view.1753

So, when the cell does work--when the electrons start to flow and we open up the circuit--the cell is doing work on something else.1767

That means that energy is leaving the system; so this is actually negative.1775

This is sort of our basic equation that we start with; this particular equation is not altogether that important; we are going to be fiddling with this a little bit.1781

Let's rearrange this and write: -W=q, times the cell potential, or the potential; and now, let's go ahead and divide by a -1; so work equals -qE.1789

So, the total work that we get is equal to...the magnitude of the work is equal to...the charge transferred, times the cell potential.1806

OK, so let me write what this is: this is the total charge transferred--the total charge that passes through the wire--all of the charge that goes through as the batter (the galvanic cell) discharges.1818

Once all of the electrons are done--no more flow--that is the total charge.1840

This is, of course, the cell potential.1845

If we multiply these two numbers, we get the actual work that the cell can do.1849

OK, now, let's talk about charge and electrons--specifically, how many electrons equal a charge--how many coulombs and electrons...what is the relationship?1855

Here is what it is: the charge on 1 mole of electrons is called a farad (after Michael Faraday), and carries a charge of 96,485 coulombs.1867

I know it's kind of a strange number; don't worry about where the number comes from.1898

So, we have 96,485 coulombs per 1 mole of electrons.1904

So now, we have a better idea of what a coulomb means, because we are very familiar with what a mole is: a mole of electrons is 6.02x1023.1915

That means, when 6.02x1023 electrons pass through that wire, that means that 96,485 coulombs of charge have passed through that wire.1925

Well, for a 1-volt cell, 1 coulomb means it has done 1 Joule of work.1938

That is the relationship: moles of electrons are related to coulombs, because coulomb is a unit of charge.1945

1 mole of electrons equals this many coulombs.1951

"Per coulomb of charge"--that is how many Joules: that is the cell potential.1955

So, for a 2-volt cell, that is 2 Joules per every coulomb of charge; well, that means every coulomb of charge has a certain number of electrons associated with it.1961

That is the relationship; so this is just another conversion factor.1975

OK, so volt equals Joules per coulomb, and a farad equals coulombs per mole of electrons: 96,485 coulombs per every mole of electron.1978

OK, now let's go ahead and put this equation together with this equation.1995

q...now, we said that work is equal to -q, times the cell potential; and we said that q was the total charge transferred.2003

That is the total amount of charge; OK.2020

That (total charge transferred) is equal to the moles of electron that are actually transferred, times the number of coulombs per mole, because moles cancel to leave us coulombs.2023

Well, q is equal to n, which is the number of moles, times F, which is 96,485 coulombs per mole.2046

So now, we can put this q in here, and we get that workmax is equal to -n, times F, times E.2057

Here we go: this was our first primary, important equation.2073

The maximum work that is possible is equal to the total number of moles of electrons that are transferred, times the farad, times the potential.2078

This gives us Joules, right?--so n is moles; F is coulombs per mole of electrons; and the cell potential is Joules per coulomb.2087

Mole cancels mole; coulomb cancels coulomb; and we are left with Joules--that is the total amount of work that is possible for us, upon that much transfer of electrons.2101

OK, now the next part: you remember when we discussed free energy--thermodynamics: the workmax is also equal to the ΔG of the particular reaction (the free energy change is equal to workmax).2110

Well, workmax is equal to free energy; workmax is equal to -nFE; what we get is: ΔG is equal to -nFE of the cell, and for standard conditions (which is--you remember--25 degrees Celsius, 1 Molar concentration, 1 atmosphere pressure for gases...)...that version...A minus nF...there we go; and this is actually cell: this is the cell potential.2127

So, what this says: the maximum cell potential is directly related to the free energy of the cell reaction.2167

There is a relationship between the balanced cell reaction, the oxidation-reduction reaction that is going to take place (it's just a reaction)...there is a relationship between the free energy of that reaction and the cell potential that we calculated based on standard reduction potentials.2201

The constant of proportionality equals the farad times the number of moles that are actually transferred in that particular reaction.2218

For example, in the aluminum-magnesium, there are 6 moles of electrons that are transferred (right?--because of the 6 electrons, we have to cancel 6); that is what this n is--it's the number of moles of electrons that are transferred per reaction.2226

This is the important equation that we want to talk about.2241

This is actually pretty great, because this actually gives us an experimental means of calculating free energies for the reactions.2245

All we have to do is basically run the reaction or calculate the cell potential; multiply by F; multiply by n; and we actually get the ΔG.2252

This is really, really great.2261

Let's finish off with an example here--Example 3: Calculate ΔG standard for the cell Mg, Mg2, Al3+, Al.2262

OK, let's calculate the free energy for this: well, when we calculated this, we got a standard: the cell potential was 0.71 volts.2290

Therefore, the ΔG standard is equal to -nFE; OK, now let me write the equations down, so we remember what we are talking about, as far as what n is going to be.2302

We had: aluminum 3+, plus 3 electrons, went to aluminum, and magnesium went to magnesium 2+, plus 2 electrons.2315

The total number of moles of electrons that were transferred (remember, we had to multiply this equation by 2 and this equation by 3): 6.2329

6 moles of electrons transferred for one cycle of this.2338

All right, it's the balanced reaction: when we balance this reaction, we get: 2 Al goes to 2 Al; 3 Mg goes to 3 Mg; 2x3 is 6 electrons--3x2 is 6 electrons.2342

Equalize the number of electrons: that is the number of moles--that is what n is.2357

So, this is going to be -6 moles...well, actually, you know what, I'm going to go ahead and write out the units.2361

-6 moles, times 96,485 coulombs per mole, times 0.71 Joules per coulomb: coulomb goes with coulomb; mole goes with mole; and we end up with ΔG=-4.11x105 Joules, or 411 kilojoules.2371

That is actually quite a lot; so, if I have a cell that is made up of aluminum and magnesium, I am going to get that much energy, maximum; that is how much work I can do: 411 kilojoules.2406

Now again, I am not going to get all of that; some of that is going to be lost as heat.2427

That is still...I can still get a fair amount of that; even if I end up with 30% of that, that is still a lot of energy that I can use up.2430

Now, some things to think about: ΔG is negative: that confirms that this is a spontaneous process.2436

A positive cell potential is a spontaneous process as written.2444

If the cell potential is positive as written, the reaction will happen without you doing anything to it.2449

We arranged it that way; that is how we want it; that is what is happening here.2455

That is a galvanic cell; it is a spontaneous discharge once you close the circuit.2459

ΔG is negative--spontaneous: so it confirms that this is the case.2464

There we go: OK, this sort of closes off our basic discussion of thermodynamics.2469

We will actually continue on in the next lesson and get a little bit deeper.2476

Until then, thank you for joining us here at Educator.com.2479

We'll see you next time; goodbye.2482

Educator®

Please sign in to participate in this lecture discussion.

Resetting Your Password?
OR

Start Learning Now

Our free lessons will get you started (Adobe Flash® required).
Get immediate access to our entire library.

Membership Overview

  • Available 24/7. Unlimited Access to Our Entire Library.
  • Search and jump to exactly what you want to learn.
  • *Ask questions and get answers from the community and our teachers!
  • Practice questions with step-by-step solutions.
  • Download lecture slides for taking notes.
  • Track your course viewing progress.
  • Accessible anytime, anywhere with our Android and iOS apps.