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Aqueous Solutions
Session Overview
| Modules | Aqueous Solutions |
| Concepts | solute, solvent, solution, solubility rules, solubility product |
| Keywords | water, mixture, colloid, ionic compound, van der Waals force, Madelung constant, suspension, dispersion, molarity, crystallization, miscibility, precipitation, equilibrium constant, saturation, conductivity, common ion effect, homogenization, Arrhenius |
| Chemical Substances | carbon tetrachloride (CCl4), potassium permanganate (KMgO4), silver chloride (AgCl) |
| Applications | water desalinization, glass manufacturing, bulk metallic glass |
Prerequisites
Before starting this session, you should be familiar with:
- The Bonding and Molecules module (Session 7 through Session 12)
- Chemistry of glasses (Amorphous Materials module), in Session 21 and Session 22
Learning Objectives
After completing this session, you should be able to:
- Define what makes an “aqueous solution.”
- Explain the behavior of ionic compounds in water.
- Calculate molarity of a solution.
- Predict the solubility of different combinations of solutes and solvents, given the chemical properties of those compounds.
- Explain the dynamics of solutions using the concepts of equilibrium constant, solubility product, and common ion effect.
Reading
| Book Chapters | Topics |
|---|---|
| [Saylor] 13.1, “Factors Affecting Solution Formation.” | Forming a solution; roles of enthalpy and entropy |
| [Saylor] 13.2, “Solubility and Molecular Structure.” | Factors affecting solubility; molecular interactions in liquids; solutions of solids; solubility of ionic substances |
| [Saylor] 13.3, “Units of Concentration.” | Molarity and mole fraction as measures of concentration |
| [Saylor] 17.1, “Determining the Solubility of Ionic Compounds.” | Solubility product Ksp, ion product, common ion effect |
| [Saylor] 17.4, “Solubility and pH.” | Acid-base equilibriua effects on solubility; basic, acidic, and amphoteric oxides; using pH for selective precipation |
Lecture Video
Resources
Lecture Summary
This session surveys the chemistry of aqueous solutions, in which ionic compounds are dissolved in liquid water as a solvent. The rule “like dissolves like” means that a solute tends to dissolve best in a solvent with similar chemical structure. Molarity is defined as a measure of solubility, and conventions for classifying substances as soluble and insoluble are presented. The session also defines and examines the importance of equilibrium constant K and solubility product Ksp, and the common ion effect.
The class ends with a discussion of the properties of amorphous glasses, including recent advances in fabrication and product manufacturing using bulk metallic glasses.
Homework
Textbook Problems
| [saylor] Sections | Conceptual | Numerical |
|---|---|---|
| [Saylor] 17.1, “Determining the Solubility of Ionic Compounds.” | 1, 6 | 2, 3, 10, 18, 21 |
For Further Study
Supplemental Readings
Chang, Kenneth. “The Nature of Glass Remains Anything but Clear.” The New York Times, July 29, 2008.
People
Session Overview
| Modules | Aqueous Solutions |
| Concepts | Arrhenius, Brønsted-Lowry, and Lewis models of acids and bases, acid strength, pH |
| Keywords | acid, base, alkali, acid-base reaction, proton, electron, donor, acceptor, neutralization, dissociation, ionization, conjugate acid-base pairs, protonation, deprotonation, amphiprotic |
| Chemical Substances | ammonia (NH3), ammonium (NH4), hydronium (H3O+), hydroxyl (OH-), acetic acid (CH3COOH), sulfur dioxide (SO2) |
| Applications | pickling, wine, coal-fired power plant, acid rain, sulfur dioxide scrubber |
Prerequisites
Before starting this session, you should be familiar with:
- the Molecules and Bonding module (Session 7 through Session 12)
- Solutions (Session 25)
Learning Objectives
After completing this session, you should be able to:
- Compare the acid-base models of Arrhenius, Brønsted-Lowry, and Lewis, and know the salient features of each.
- Write the general acid-base reaction.
- Explain the chemical basis of acid strength and the pH measurement.
- Describe the behaviors of conjugate acid-base pairs.
- Explain how dissociation affects ionic compounds.
- Solve specific acid-base reaction problems.
Reading
| Book Chapters | Topics |
|---|---|
| [Saylor] 4.6, “Acid-Base Reactions.” | Definitions of acids and bases; polyprotic acids; strengths of acids and bases; hydronium ion; neutralization reactions; pH scale |
| [Saylor] 8.7, “Lewis Acids and Bases.” | Lewis acids and bases |
| [Saylor] 16.1, “The Autoionization of Water.” | Acid-base properties of water; ion-product constant; relationship among pH, pOH, and pKw |
| [Saylor] 16.2, “A Qualitative Description of Acid-Base Equilibria.” | Conjugate acid-base pairs; equilibrium constants Ka, Kb, pKa and pKb; strong acids and bases; leveling effect; polyprotic acids and bases; solutions of salts |
| [Saylor] 16.3, “Molecular Structure and Acid-Base Strength.” | Bond strengths; conjugate bases; inductive effects |
| [Saylor] 16.4, “Quantitative Aspects of Acid-Base Equilibria.” | Ka and Kb; percent ionization from Ka and Kb; Keq from Ka and Kb |
Lecture Video
Resources
Lecture Summary
This lecture introduces the chemical models and behaviors of acids and bases. Starting from the historical origins (“acid” derives from the Latin acidus, meaning “sour”), Prof. Sadoway discusses the evolving acid-base models of Lavoisier (1776), Arrhenius (1887), Brønsted and Lowry (1923), and Lewis (1923-1938).
The lecture proceeds to cover:
- The general acid-base reaction
- Conjugate acid-base pairs
- The dissociation process of ionic compounds
- Solving acid-base reaction problems
Homework
Textbook Problems
| [saylor] Sections | Conceptual | Numerical |
|---|---|---|
| [Saylor] 4.6, “Acid-Base Reactions.” | 1, 2 | none |
| [Saylor] 16.2, “A Qualitative Description of Acid-Base Equilibria.” | 2 | 2 |
| [Saylor] 16.3, “Molecular Structure and Acid-Base Strength.” | 3 | none |
| [Saylor] 16.4, “Quantitative Aspects of Acid-Base Equilibria.” | none | 8, 15 |
| [Saylor] 16.5, “Acid-Base Titrations.” | none | 1 |
| [Saylor] 16.6, “Buffers.” | none | 3 |
For Further Study
Supplemental Readings
Djerassi, C., and R. Hoffmann. Oxygen: A Play in Two Acts. New York, NY: Wiley-VCH, 2001. ISBN: 9783527304134. See also the study guide and other publisher resources.
Brandis, Kerry. Acid-Base Physiology. See Chapter 1 of this online tutorial/textbook, which applies acid-base chemistry to physiology.
People
Svante Arrhenius — 1903 Nobel Prize in Chemistry
Other OCW and OER Content
| Content | Provider | Level | Notes |
|---|---|---|---|
| 5.111 Principles of Chemical Science | MIT OpenCourseWare | Undergraduate (first-year) |
For an alternative treatment of many topics in this session (e.g. acid-base models, pH, equilibrium, acid strength, reaction problems), see: |
| Acid-Base Equilibrium | Connexions | Undergraduate, general chemistry | Includes notes and sample exercises |
This self-assessment page completes the Aqueous Solutions module, and covers material from the following sessions.
- Session 25: Introduction to Aqueous Solutions
- Session 26: Acids & Bases
On this page are a simple weekly quiz and solutions; relevant exam problems and solutions from the 2009 class; help session videos that review selected solutions to the exam problems; and supplemental exam problems and solutions for further study.
Weekly Quiz and Solutions
This short quiz is given approximately once for every three lecture sessions. You should work through the quiz problems in preparation for the exam problems.
Exam Problems and Solutions
These exam problems are intended for you to demonstrate your personal mastery of the material, and should be done alone, closed-book, with just a calculator, the two permitted reference tables (periodic table, physical constants), and one 8 1/2" x 11" aid sheet of your own creation.
After you’ve taken the exam, watch the help session videos below for insights into how to approach some of the exam problems.
Exam Help Session Videos
In these videos, 3.091 teaching assistants review some of the exam problems, demonstrating their approach to solutions, and noting some common mistakes made by students.
Clip 2: Final Exam, Problem 10
Supplemental Exam Problems and Solutions
These additional exam problems from prior years’ classes are offered for further study.
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