Enter your Sign on user name and password.

Forgot password?
Sign In | Subscribe
Start learning today, and be successful in your academic & professional career. Start Today!
Use Chrome browser to play professor video
Raffi Hovasapian

Raffi Hovasapian

Galvanic Cells

Slide Duration:

Table of Contents

I. 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
II. 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
III. 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
IV. 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
V. 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
VI. 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
VII. 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
VIII. 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
IX. 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
X. 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
XI. 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
XII. 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
XIII. 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
XIV. 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
XV. 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
XVI. 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
  • Discussion

  • Study Guides

  • Download Lecture Slides

  • Table of Contents

  • Transcription

  • Related Books & Services

Lecture Comments (21)

1 answer

Last reply by: Professor Hovasapian
Mon Apr 23, 2018 3:37 AM

Post by Immanuel Wilson on April 20 at 10:35:48 AM

Hey Professor Hovasapian, I think there's something wrong with this video. It only plays until about the 9-minute mark.

1 answer

Last reply by: Professor Hovasapian
Thu Nov 17, 2016 6:18 AM

Post by Joseph Mcginley on November 9, 2016

Hi, I have a question about salt bridges, if the salt is supposed to balance the charges of the solutions and therefore extend the length of time current is flowing, what happens when there are no more electrons to flow from the side that's giving them? Is that when the reaction and the current stop?

1 answer

Last reply by: Professor Hovasapian
Tue Jun 28, 2016 9:00 PM

Post by Neil Kotta on June 28, 2016

Oh okay I think I see what you mean...could we just look at the reduction potentials in this case or no? Thank you so much for helping me

3 answers

Last reply by: Professor Hovasapian
Wed Jan 18, 2017 7:39 PM

Post by Neil Kotta on June 28, 2016

In example three how is PO3(3-) oxidized? I thought it gained electrons there making it a reduction reaction not an oxidation. Thank you

1 answer

Last reply by: Professor Hovasapian
Fri Apr 1, 2016 2:50 AM

Post by Sazzadur Khan on March 30, 2016

On example 3, which direction is the electron flow and why?

1 answer

Last reply by: Professor Hovasapian
Tue Dec 2, 2014 2:42 AM

Post by Long Tran on November 30, 2014

Hi Professor,
thank you for the lecture, i understand the process to break the reaction into 2 half rxn. However, i have difficulty to do the half rxn of this rxn. i hope you can help
O2(g) + 4H+(aq) + 4Fe2+(aq) -----> 4Fe3+(aq) + 2H2O(l)

2 answers

Last reply by: Christian Fischer
Thu May 15, 2014 1:29 AM

Post by Christian Fischer on May 12, 2014

Hi raffi. Great lecture on redox chemistry - I really needed to refresh this. A quick question: When you add OH(-) at about 11.30min, do you allways add the same amount of OH(-) as the amount of H(+) added on each side in order to neutrulize the H+? And do you always add the same amount of OH(-) on the left and right side of the reaction?

Kind regards
Christian  

3 answers

Last reply by: Professor Hovasapian
Fri Sep 27, 2013 5:28 PM

Post by Nithist kanjanavikai on September 22, 2013

Excuse me. In min 12:26, why does the left side of the equation has PO4^3-?

Galvanic Cells

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
  • Galvanic Cells 0:39
    • Example 1: Balance the Following Under Basic Conditions
    • Example 1: Steps to Balance Reaction Under Basic Conditions
    • Example 1: Solution
    • Example 2: Balance the Following Reaction
    • Galvanic Cells
    • Example 3: Galvanic Cells
    • Example 4: Galvanic Cells

Transcription: Galvanic Cells

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

Last time, we introduced the notion of oxidation-reduction chemistry as a sort of an entry into our discussion of electrochemistry.0004

We talked about the balancing of an oxidation-reduction reaction (otherwise known as a redox reaction) under acidic conditions.0012

So, today I am going to give you an example of how to balance it under basic conditions, because as it turns out, reactions--for redox, they can either happen under basic, neutral, or acidic conditions.0020

Let's just go ahead and jump into the example, and we will go through what it is that we are doing as we go along.0033

OK, so the first example: we want to balance the following reaction under basic conditions.0040

Let me write: Example 1: OK, balance the following under basic conditions.0047

And "basic conditions" just means hydroxide; so, somewhere along the way, we are going to add hydroxide to see...because remember, in "under acidic conditions," one of the things on one side or the other of the reaction was some hydrogen ion; that is the acid.0062

Under basic conditions, your base is going to be the hydroxide ion.0077

If you end up doing something under basic conditions, and you realize that there is no hydroxide anywhere, something is wrong; something happened.0082

OK, under basic conditions: So we have: PO33- (this is phosphite, by the way) + MnO4- goes to MnO2 (this is a solid) + PO43-.0091

These ions are all going to be aqueous; that is the whole idea behind ions--these are aqueous solutions.0115

Sometimes, though, you are going to end up with some solids or some gases, and we will specify whether they are solids or gases.0119

But, I'm not going to go ahead and put "aq" underneath each of these; when you are dealing with ions, you are talking about an aqueous solution (water); that is it.0126

OK, well, clearly, this is an oxidation-reduction reaction, because here, the phosphorus (PO3) goes to PO4 (right?--phosphorus becomes oxidized).0134

The oxidation states--you can confirm this by doing oxidation states: you know, let's just go ahead and do it while we are here.0145

Oxygen is a -2 oxidation state; there are 3 of them, for a total of -6; -6, plus what number, will give us a +3?0151

So here, phosphorus is a +3 oxidation state; over here, oxygen is -2; there is a total of 4 of them, so the total charge is -8; -8, plus what, will give us a -3?0163

Remember, the sum of all of the oxidation states of all of the individual atoms add up to the charge on the species.0175

In this case, the charge on the species is 3-, so this is 5+; so this is oxidized from a +3 to a +5--it loses two electrons.0183

Well, manganese--here, this is a +7, and this is going to end up being a +4; here, it gains three electrons.0193

So, the electrons don't balance; but we'll work that out as we go through.0203

Here are the steps for balancing an oxidation-reduction reaction under basic conditions.0206

OK, step 1 (you are going to like this): do the same thing as you did for acid conditions.0213

I'm going to write the steps, and then I'm going to do them.0236

OK, step 2: once you do that (once you balance the reaction under acidic conditions), now, add equal amounts of OH- to each side of the reaction to balance out the H+--because, if you do it under acidic conditions--the first part--you are going to have some H+ left over.0238

Well, we want to neutralize that H+ with an equal amount of OH-, but we want to do it on both sides, so that one side ends up with water and the other side ends up with the hydroxide.0280

Step 3: eliminate H2O if it occurs on both sides (which we do anyway; any time we have two species on the same side of an equation, we cancel them out like we do in algebra, if it occurs on both sides).0291

And number 4: Check.0316

That is it; so let's go ahead and do this.0320

So, we take a look; we use the assigning of oxidation states to decide that phosphorus is going to be oxidized, manganese is going to be reduced; so, let's write our two half-reactions.0323

I tend to do my reduction first--just personal choice; it doesn't really matter--actually, sometimes I even do the other way first.0337

But, let's do...so we have MnO4- going to MnO2.0346

OK, so the first thing we do (again, first step, right here--right now we're doing this one): we do the same thing as for acidic conditions.0356

We write down the reduction reaction; let's go ahead and balance this one.0364

The manganese are already balanced: 1 Mn, 1 Mn; we have 4 oxygens on the left; we have 2 oxygens on the right; so we balance that with 2 waters (remember, we use waters to balance the oxygens).0368

Well, in the process of balancing the oxygens, we have introduced, now, 4 hydrogens; so we come over here, and we add 4 hydrogens to balance the hydrogens.0381

Now, we have to balance the charge, the electrons.0393

This is 0 net charge over here; here we have 4 positive, 1 negative--that gives us 3 positive, so we need to add 3 electrons to the left to balance out the charge.0396

This one is balanced; let me go ahead and put a little bracket around it--this is our reduction half-reaction.0412

That is what we are doing: we are breaking it up into 2 half-reactions: a reduction half reaction and an oxidation half-reaction.0418

We are balancing each; then, we are adding everything and canceling species.0424

OK, now the oxidation part: in the oxidation part, we have: PO3- (and remember, write every species) goes to PO4-: phosphite goes to phosphate.0428

Well, 4 oxygens, 3 oxygens; so let's go ahead and add a water over here--that gives us 4 oxygen.0442

We have introduced two hydrogens (oops, here we go with the...oh, I'm going to erase this; I'm not going to have these lines all over the place; I do not like that).0450

OK, oxygen: let's try again: PO33- to PO43-; so, we said we added a water molecule; so here, we have to add two H+s to go ahead and balance the hydrogens.0459

Now, we are going to balance the charge.0480

We have a 3- and a 0, for a total of 3- on the left; we have 3- and 2+ on the right...so 3-, plus 2, is a -1; so we have -1 on the right, and we have -3 over here; so here, we need to add two electrons.0481

There we go; this is our balanced oxidation half-reaction.0504

OK, now the next thing (again, we are still in step 1) we do is: we want to be able to cancel the electrons, so we have to multiply each equation, or one equation, by integers, to make sure that the electron count equalizes.0512

3 electrons on the left; 2 electrons on the right; so I'm going to multiply this equation by 2 (let me do this in red)--everything by 2--and this equation by 3.0526

OK, and now I'm going to rewrite these two equations: so I'm going to get 2 MnO4- + 8 H+ + 6 electrons goes to 2 MnO2 + 2 H2O...I'm sorry, 4 H2O (because it's 2 times 2, right?--yes, even we make mistakes).0540

And this one down here becomes: 3 H2O + 3 PO43- goes to 3 PO43- (my apologies; this is PO33-; wow, we have superscripts; we have subscripts; we have coefficients--all kinds of symbols going on here...where are we?) + 6 H+, and 6 electrons.0570

Now, we add these; when we add this, let's see: 6 electrons cancels 6 electrons; 3 H2O cancels 4 H2O, leaving just 1 H2O; 6 H+ cancels 8 H+, leaving 2 H+.0602

So, our final should be something (well, so far; final of step 1)...is going to be 2 MnO4- + 2 H+ + 3 PO33- goes to 2 MnO2 + 3 PO43- + H2O.0622

OK, so now, we are done with step 1.0655

We have balanced each half-reaction; we have added; we have canceled the species; now, we are going to go to step 2--we are going to have to add hydroxide to both sides.0658

Let me rewrite the equation again: so, I have: 2 H+ + 3 PO43- + 2 MnO4- goes to 3 PO43- (the order doesn't matter, so don't feel like it has to be in a certain order; it doesn't) + 2MnO2 + H2O.0665

OK, so we have that; now, our second step was: we want to add an equal amount of hydroxide to cancel out the hydrogen ion.0694

We have two hydrogen ion over here, so I'm going to add 2 hydroxide ions...+ 2 hydroxide ions, to both sides.0701

OK, when we combine this, the H+ and the OH- combine to form 2 H2O + 3 PO43- (I'm going to write everything...you can do this without writing everything again and again, but I want you to see the steps) → 3 PO43- + 2 MnO2 + H2O + 2 OH-.0714

Well, now we have 2 H2O here; one H2O; so that H2O goes with that H2O, leaving only one water.0740

Our final is one water on the left, plus three phosphite ions, plus two permanganate ions, goes to three phosphate ions, plus two manganese dioxide (this is a solid), plus two hydroxides.0746

Here we go: this is our final balanced equation for basic conditions.0768

What that means is this--so let me tell you what this means, because there is a lot of symbolism here: This means that, if I put together--if I mix--some phosphite ion with some permanganate ion, the manganese is going to oxidize the phosphorus.0774

The MnO4 is going to turn into manganese dioxide; it's going to be a solid; it's going to drop to the bottom of the beaker if I just mix these two.0793

The phosphite is going to turn into phosphate; it's going to grab one of the oxygens that comes from the water, or maybe just one of these oxygens here.0800

There has to be some water floating around for this to happen; that is why this water is here.0809

If there is no water to make this happen, this won't happen.0814

In the process, we end up creating two hydroxide ions.0817

That is what this says.0825

OK, it's a basic oxidation-reduction reaction; this is how we balance it under basic conditions.0828

Good; OK, now there is one more that I would like to show you; this one is actually really, really easy.0835

I'll call this one Example 2 (let's go back to blue): Balance Zn2+...if I take zinc ion, and if I add some aluminum metal to that zinc ion solution, I end up with aluminum ion solution, and all of a sudden, zinc metal starts to show up in the solution.0841

So, in other words, aluminum dissolves, and zinc shows up; it will happen.0866

So, here is the reaction; we want to balance it.0873

Well, we want to balance it: we do the same thing, oxidation-reduction half-reactions.0878

We balance the oxidation; we balance the reduction; we add them.0882

This looks kind of simple, because there are not a lot of oxygens and hydrogens floating around, and it's exactly what is going to happen.0886

Notice: zinc is going from zinc 2+ to zinc metal; this is reduced.0892

OK, it is going from an ion; it's going to the metal; so, the reduction part is going to be: zinc 2+ going to zinc.0896

How does that happen?--well, we add two electrons to the left; this is the reduction part (let me put a bracket around it, which is my way of dealing with oxidation-reduction reactions).0912

The oxidation: aluminum is losing three electrons to become aluminum 3+.0923

So, we write: aluminum, aluminum 3+; oxidation is written with the electrons on this side.0928

Let me make this a little better, too...0938

This is the oxidation half-reaction; these electrons are not equalized--we need to multiply them.0944

Now notice, there is no...1 Zn, 1 Zn; 1 Al, 1 Al; I'm still using the same process: balance the oxygens with H2O...there are no oxygens; balance the hydrogens...no hydrogens; balance the charge...we did--we added the electrons.0949

OK, everything is good; now, we just multiply by integers to equalize the electron count.0964

I'm going to multiply this equation by 3, and I'm going to multiply this equation by 2.0969

I'm going to get: 3 zinc ion, plus 6 electrons, goes to 3 zinc metal; and I have: 2 aluminum metal goes to...becomes...2 aluminum 3+ ion, plus 6 electrons.0973

Now, we add them; the electrons cancel, and I am left with: 3 Zn + 2 Al goes to 3 Zn, solid (this is solid) + 2 Al3+ (and the ions, we said, are aqueous).0996

So, here is what happens: if I have some solution of, let's say, zinc sulfate--I have a bunch of zinc 2+ floating around and SO42- floating around--if I take a piece of aluminum and I actually drop it in here--just take a solid chunk of aluminum and I drop it in there--guess what is going to happen.1016

The aluminum is going to melt, and where the aluminum is melting, zinc is going to show up--because this says that it will.1036

We will get to (in the next lesson) how we know that this will happen; we are going to assign numbers to these things and decide, if I mix this with this, which one is going to melt and which one is not.1049

We will decide later, but right now, we are just working with balancing the reactions; but I want you to see what "balancing reaction" means.1061

Zinc metal--3 atoms of zinc metal--react with 2 (zinc ion; I'm sorry--this is 2+) atoms of aluminum metal; they rip electrons away from the aluminum--3 electrons from each aluminum atom; each zinc takes 2 of those electrons to become zinc metal, and it leaves the aluminum metal to go into solution.1069

That is what is happening.1092

OK, so now, we can move on, and we can actually get into electrochemistry.1094

We are going to start off by discussing this thing called a galvanic cell, also called a voltaic cell.1099

You will hear them referred to as both; I'm going to call it a galvanic cell.1107

Let's see: now, let's look again at the reaction (well, you know what, let me write it below) 8 H+ + MnO4- + 5 Fe2+ goes to Mn2+ + 5 Fe3+ (the ferrous ion goes to ferric ion and produces four molecules of water in the process).1111

Now, as we said, if I take some iron ion solution--iron 2+ ion solution--and I mix it with some permanganate solution, and if I add some acid to get things going, this reaction is going to take place.1153

The manganese is going to steal electrons from these iron atoms; it's going to become manganese 2+; it is going to release those oxygens.1170

Those oxygens are going to bind with the hydrogen in a shift of electrons being moved around among all these species; four water molecules are going to form, and the iron (2) is going to turn into iron (3).1178

That is what is going to happen if I just mix them.1190

Well, what happens if I take these two solutions--the permanganate solution and the iron solution--and I keep them in separate beakers?1193

Well, let's see what happens.1200

If I take that and that--so I have this solution of MnO4- with a little bit of H+ thrown in for good measure, and here I have a solution of Fe2+...1203

It could be iron sulfate, iron chloride...we don't really care about the anion; it's the cation that is important in this particular case, and here, this could be potassium permanganate, calcium permanganate...it doesn't really matter--here it's the anion that matters, so we're interested in the species that are involved in the chemistry.1219

If I put these two solutions together, and if all of a sudden, I decide to take some metal wire (like some platinum wire or something), and if I connect them with a wire, what is going to happen?1236

Well, as it turns out, this reaction will take place; and the reason it will take place is because now, the electrons...before, when they were in the same beaker, the electrons just transferred face-to-face; here, if I connect them with a wire, the electrons have a path.1247

In other words, the manganese still wants the electrons that iron has to give up; therefore, it will take them from the iron; but the electrons will actually travel through the wire.1265

This oxidation-reduction reaction will take place, and it will take place spontaneously, because as written, this actually is a spontaneous reaction (and we will discover why later).1277

But, that is the whole idea; so, the oxidation reaction still takes place, but now, the electrons are passing through the wire.1287

Well, whenever we have electrons passing through a wire--whenever we have a current--we can use that current to do work.1298

That is the whole idea behind a galvanic cell.1305

We take an oxidation-reduction process as written; we separate the oxidizing agent and the reducing agent (we don't even need to call them that--we can just say we separate one species from the next); and we connect those two with a wire.1308

When we do that, we actually create a current; electrons spontaneously start to flow from here to here.1324

Iron gives up its electron; the electron travels through the wire; it hits the manganate ion; the manganese takes the electrons, one at a time; and once it has taken a certain number of them (5 of them, in this case), it will turn into manganese 2+.1332

So, in this compartment, manganese 2+ will start to show up; in this compartment, as iron 2+ gives up its electron, it turns into iron 3+.1347

This reaction takes place through the wire.1358

We are taking an oxidation-reduction process; we are separating the species--the oxidizing and reducing agents; we are connecting them with a wire; and we are creating a current.1362

We are going to use that current to do work; this is a battery.1371

Every single battery that you know of (cell phone, computer, flashlight, anywhere)--this is how it works.1375

Every single battery consists of an oxidizing agent and a reducing agent that are separated.1381

When you put that battery into your component, and you flip that component on, what you have done is this: you have closed the circuit.1386

The minute you close the circuit, electrons start to flow, and your thing works--it works--it works.1393

Well, there are only going to be so many electrons that you can get, right?1400

Once the electrons run out, once this thing--the thing that is being oxidized--electrons are being taken away from it--once it has no more electrons to give up, guess what: your battery is dead.1403

That is all it is--this is a battery; a galvanic cell is a battery; it's a fancy word for a battery.1414

OK, well, something interesting happens when I actually do this: it's true, electrons do flow; but they only flow for about a second, and all of a sudden, the electrons stop flowing; why is that?1420

Well, here is why: notice, electrons are flowing from this chamber to this chamber; so electrons are gathering over here.1432

There is going to be a buildup of negative charge over here.1439

Electrons are leaving this chamber, so there is going to be a buildup of positive charge over here.1442

Well, separating charges, from a physical standpoint--it takes a lot of energy to do that; charges don't like to be separated.1447

Therefore, we need to find a way to balance this charge and this charge as they are forming--as electrons are flowing.1456

We can do that two ways: we can build something called a salt bridge, or we could put something in between them, which is a porous disk.1464

A porous disk is a disk that allows certain ions to pass, but doesn't allow other things to pass.1476

Let me draw these out--the two possibilities.1482

A salt bridge is just a piece of glass tubing where, inside, there is a strong electrolyte (it could be sodium chloride, potassium chloride, calcium chloride); and what it does is: as electrons flow, and negative charge...well, let me draw it out, and you'll understand; otherwise, it's not going to make sense.1486

Everything looks exactly the same--absolutely exactly the same.1507

We have a little wire running like that; I haven't drawn in any things called electrodes, but I'll draw them in just a moment.1512

We have MnO4-, and we have H+; we have Fe2+, and we have this thing (actually, I'm going to write my MnO4- and H+ over here)--I have this tube, this glass tube, shaped like a U.1521

Inside, there is a strong electrolyte--in other words, a salt in a Jell-O-like matrix, in a soft matrix; and here is what happens.1544

When electrons flow this way, negative charge gathers over here; positive charge gathers over here; but as negative charge gathers over here, the positive ions of the strong electrolyte flow into the solution to balance the negative charge.1556

And here, as positive charge gathers on this side, the negative ions flow into solution here from the electrolyte, to balance the charge.1572

What this salt bridge does: it allows the passage of free ions to make sure that the charges are always balance, so there is not a buildup of charge; that takes a lot of energy to keep the charge separation.1581

We don't want to do that--well, it won't do that, physically.1596

As electrons flow this way, some ions flow this way; some ions flow this way; the circuit is complete--that is the whole idea.1599

It's about completing a circuit--ions travel to balance charge to make sure that the electrons keep flowing; as long as the charge maintains a 0 here, 0 here, everything is fine.1609

This is a complete description of a galvanic cell.1620

Now, I'm going to draw the version that adds the porous disk in it.1623

In this particular case, you actually separate the solutions--they are almost in contact with each other, but there is this disk in between.1627

The only difference is that it allows the passage of these ions that balance charge.1634

For all practical purposes, this salt bridge and this porous disk shouldn't really concern us; the only thing you should know about them is that they are there simply to allow the passage of ions to balance charge as electrons flow.1640

That is all; other than that, everything is exactly the same.1654

MnO4-, H+, Fe2+...there are other ions floating around, positive and negative, that allow the flow of ions across this way and across that way, to make sure that, when electrons are flowing like that, negative charge builds up here; positive charges will flow across the ion, the porous disk, to balance.1659

And here, as positive charge builds up, negative ions will pass across the disk; water will not; the ions will, to balance the charge; that is all that is going on.1680

OK, so now, let's move on to a little bit more.1691

OK, so let's do this one as an example--I think that will be the best.1698

So, we'll do Example 3: OK, in the reaction of phosphite, of PO33-, with MnO4-...which...I'll remind you what that was: we have H2O + PO33- + MnO4- goes to 3 PO44- + MnO2, solid, plus 2 hydroxide; remember, this was in basic conditions...1705

So, for this example, we would like you to draw the galvanic cell, and identify the components.1749

OK, so now, we are going to get a little bit of vocabulary work on what a galvanic cell is and what each of these things is called.1766

OK, so I'm going to draw it with a porous disk; I think it's just easier to draw than with a salt bridge.1773

That is pretty much the standard nowadays--to use porous disks; salt bridges are sort of a little further back in time.1778

OK, so we have: there we go--phosphite is the thing that is oxidized; permanganate is the thing that is reduced (it is actually the manganese that is reduced, and it's the phosphorus that is oxidized--oxygen is still -2 oxidation state).1785

I'm going to draw this: here is our porous disk; OK.1808

We are going to have a wire, and we are going to have, at the ends of the wires...we have these things called electrodes; and electrodes are usually broad pieces of metal (they could be long; sometimes they are not long, but they are generally flat); they are used to increase the surface area.1814

So, because you have this broad piece of metal, it is more in contact than actually just a thin wire is; so there is more opportunity for reactions to take place, like that.1832

If you had just a wire, it's only this much; but if you had this, it's all the space available on the...so these things are called...electrodes.1842

OK, they are the things at the ends of the wire that are actually dipped into these liquid solutions; they are called electrodes.1851

OK, and in this particular case, they are actually platinum electrodes; more often than not, platinum is used.1855

Now, the reason...we will actually talk a little bit about why we use these platinum electrodes in some of the other galvanic cells that we draw in just a little bit.1861

We are actually going to use electrodes made of the metals themselves, that are being oxidized and reduced.1883

But, in this case, because none of the species that is actually being oxidized or reduced is a metal in and of itself, it can't be used as an electrode.1888

We have to use some inert material--so basically a scaffold--someplace where the reaction can take place.1897

You notice: this is an aqueous ion; this is an aqueous ion; in order for them to react, they have to somehow come together.1904

Well, the surface of a nice, inert metal like platinum allows them a place for them to conduct business, if you will.1911

That is really all these electrodes do: it allows these aqueous ions to conduct their business, and it gives them a place to do that.1918

OK, so let's see what happens: that is the platinum electrode; let's go ahead and put...for the time being, it doesn't really matter where we put our solutions.1926

PO33-...I'll put my phosphite solution there; and I'll put my permanganate solution over here (MnO4-), and we also have some hydroxide, right?--that is over here.1937

Here is what is going to happen: we know that phosphite is oxidized; we know that permanganate is reduced; well, that means the thing that is oxidized...electrons are going to flow...so I'm going to write...1955

You know what, I'm going to rewrite this: I'm going to write PO33-, MnO4-.1967

Here is what happens: an electron is stolen from phosphorus, travels through the electrode, and travels through the wire in this direction.1982

It comes down here, and at the interface, it jumps onto the manganese.1995

When enough of these electrons jump onto the manganese, what happens is that manganese dioxide starts to form on the electrode's surface, because this reaction is taking place on the electrode's surface.2000

This solution is in contact with this metal; where the ion meets the metal, that is where it releases its electron and lets it go.2016

As it releases its electron, there is water here; so it's going to turn into PO4; as this one is reduced, manganese dioxide is a solid, and it's going to start forming on the electrode, like that.2025

This is called the anode; anode is where oxidation takes place; this is what is important: where oxidation takes place, it's called the anode.2044

The best way to remember this: oxidation is a vowel; anode begins with a vowel.2059

That is the best way to remember that; that is still how I remember it.2064

Over here, this is called the cathode; the cathode is where reduction takes place.2067

In other words, it is where the electrons come to--where reduction takes place.2075

That is all that is happening here: something is being oxidized--it is giving up electrons; electrons are moving away from that area--they are being sucked over into here, because now, this one is going to take the electrons and use them.2081

This is being oxidized; this is being reduced; where oxidation takes place, this is called the anode; where reduction takes place, this is called the cathode.2093

That is it--where reduction takes place.2105

I hope that makes sense.2110

OK, now let's do another one--Example 4: Let's use our 3 Zn2+ + 2 Al goes to 3 zinc metal, plus 2 Al3+.2112

So, notice what is happening here: zinc ion is turning into zinc metal; aluminum metal is turning into aluminum ion.2141

Because the metals are actually there as species, one of them is becoming a metal; one of the metals is turning into...you can actually use these metals as the electrodes.2149

You don't have to use platinum; you don't have to use some inert...the only time that you need some inert platinum electrode is when the things being oxidized and reduced are aqueous ions, and they stay aqueous ions.2162

In this case, what this looks like is the following.2174

This is the water level, by the way, so I should make it like this; this is just...that's right.2182

What this looks like is: there we go--for the time being, it doesn't matter where we put what, so how about if I put the aluminum...how about if I make this the aluminum metal, and if I make this the zinc metal.2187

That means here I have zinc ion in solution, and here I have aluminum ion in solution; and I actually may not have any aluminum ion in there yet.2205

What ends up happening is the following: zinc is being reduced; aluminum is being oxidized; well, here is the aluminum--it is oxidized; oxidation--anode, so this is the anode; this is the cathode.2213

Oxidation is where electrons are lost; that means this aluminum metal--electrons are being pulled from the aluminum metal, and they are traveling through this wire.2229

When they arrive here, they attach themselves to zinc ion that is touching the metal surface, and zinc metal starts to form on top of the zinc electrode.2240

That is why, because it's a metal, we can actually use it as the electrode; so zinc metal starts to form, and this aluminum starts to break down; the aluminum starts to dissolve.2257

When aluminum gives up its electrons, it turns into aluminum ion; so now, a whole bunch of aluminum ion is going into solution.2272

The metal is turning into the ion; here, the zinc ion is turning into the metal.2281

That is what is happening.2285

OK, now, let's see: let me write down: When the species being oxidized is a metal and/or the species being reduced becomes a metal (like this--aluminum is oxidized; it's a metal; zinc is the species...it's becoming a metal: we can go ahead and use those metals as the electrodes; you don't have to use platinum), then the electrodes can be the metals themselves.2288

OK, remember what we just said: aluminum metal--zinc wants the electrons; electrons disappear...an aluminum atom loses its electrons; the electrons flow this way.2362

When it loses its electrons, it becomes aluminum ion; therefore, aluminum ion goes into solution.2378

That is what is happening.2386

Zinc is forming: at this interface where the zinc metal is in contact with the zinc ion solution, the ions grab the electrons.2388

The minute they grab the electrons, the zinc 2+ becomes...they grab 2 electrons; they become zinc 0.2397

It becomes zinc metal; so zinc metal starts to form on top of the zinc metal electrode.2403

This starts to dissolve; now, this process right here--this metal dissolving--this is what happens when a metal dissolves in acid.2408

This is an oxidation-reduction reaction; as it turns out, when you drop a metal into acid (like, for example, if you drop zinc into acid or aluminum into acid), what is going to happen is an oxidation-reduction reaction.2419

So, I want you to be able to see this: so this--when metals dissolve in acid (not all metals do), this is an oxidation-reduction reaction, not an acid-base reaction like you might think.2434

Just because an acid is involved, in this particular case it doesn't mean it's an acid-base reaction.2472

Well, here is what is happening: if I take zinc metal, and I drop it into acid, zinc gets oxidized.2476

In other words, zinc loses 2 of its electrons, and it turns into zinc ion, plus two electrons.2482

That metal--that zinc metal--dissolves; and it is dissolving because the metal is turning into zinc ion, and the zinc ion is going into solution.2494

Well, if zinc is oxidizing, then what is reducing?2502

As it turns out, hydrogen ion--the acid itself--is reducing.2505

Hydrogen ion--the acid in solution--actually grabs onto those two electrons; two hydrogen ions grab onto that, and what do you think it becomes?--it becomes hydrogen gas.2511

Those are the bubbles that you see when you drop a metal into acid.2522

When you drop a metal into acid, the hydrogen ion wants the electrons stronger than the zinc does; it rips those electrons away from zinc.2525

Zinc goes into solution (in other words, it dissolves--it melts); hydrogen ion grabs those two electrons.2533

Each hydrogen ion takes one electron; so now, you have two hydrogen atoms--hydrogen atoms that are in proximity to each other--they bind; they form hydrogen gas.2539

That gas bubbles off: that is what you see.2549

So, when you put acid on some sort of organic substance, it will melt--it will dissolve--but that is an acid-base reaction--that is the transfer of protons.2553

When you drop a metal into acid, this is an oxidation-reduction reaction; they have the same physical effect (things dissolve), but it's completely different chemistry.2563

It's really, really important to understand that.2574

This is sort of the key; and this reaction right here will become very, very important in our next lesson, when we discuss something called standard reduction potentials.2576

So, until then, thank you for joining us here at Educator.com.2585

We'll see you next time; goodbye.2588

Educator®

Please sign in for full access to this lesson.

Sign-InORCreate Account

Enter your Sign-on user name and password.

Forgot password?

Start Learning Now

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

Sign up for Educator.com

Membership Overview

  • Unlimited access to our entire library of courses.
  • 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 lesson files for programming and software training practice.
  • Track your course viewing progress.
  • Download lecture slides for taking notes.