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CHEM102: General Chemistry II

Unit 2: Solutions and Chemical Equilibrium   We are now approaching the topic that most people think of when they hear the word “chemistry,” where we pour one clear solution into another clear solution to produce a purple solution, or add a pink solution to an orange solution to make a clear solution.  Though these transformations may seem like a magic trick, they actually depend on the properties of solution chemistry, solubility, and chemical equilibrium—all of which will be discussed in this unit.

2.1 Chemical Equilibrium   - Reading: General Chemistry Virtual Textbook: Stephen Lower’s notes on Introduction to Equilibrium Link: General Chemistry Virtual Textbook: Stephen Lower’s notes on Introduction to Equilibrium (HTML)

 Also available in:  
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 Instructions: Please read this section, which provides an in-depth
explanation of reversible reactions and the concept of
equilibrium.  

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2.1.1 Le Chatelier’s Principle   - Reading: Aus-e-Tute’s notes on Le Chatelier’s Principle Link: Aus-e-Tute’s notes on Le Chatelier’s Principle (HTML)
 
Instructions: Please read this section beginning with the title Le Chatelier’s Principleto gain a general understanding of the key concepts behind the principle and its application in equilibrium chemistry.  

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  • Reading: General Chemistry Virtual Textbook: Stephen Lower’s notes on Le Chatelier’s Principle Link: General Chemistry Virtual Textbook: Stephen Lower’s notes on Le Chatelier’s Principle (HTML)
     
    Also available in:
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    Instructions: Please read this section, which provides a mini biography on Le Chatelier and several examples illustrating the key concepts of the principle.

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2.1.2 Reaction Quotient and Equilibrium Constant   Note: When reaction quotient Q is equal to K, we have equilibrium.  If Q is less than K, the reaction favors products.  The contrary is true when Q is greater than K.

  • Reading: Purdue University Chemistry: William R. Robinson’s notes on Writing Equilibrium Expressions Link: Purdue University Chemistry: William R. Robinson’s notes on Reaction Writing Equilibrium Expressions (HTML)
     
    Instructions: Please read this section to gain a general understanding of how to determine equilibrium constants.
     
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  • Reading: General Chemistry Virtual Textbook: Stephen Lower’s notes on Writing Equilibrium Expressions Link: General Chemistry Virtual Textbook: Stephen Lower’s notes on Writing Equilibrium Expressions (HTML)
     
    Also available in:
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    Instructions: Please read this section and then complete the problems included.

    Terms of Use: This resource is licensed under a Creative Commons Attribution-ShareAlike 3.0 Unported license.

  • Reading: General Chemistry Virtual Textbook: Stephen Lower’s notes on The Difference Between Q and K Link: General Chemistry Virtual Textbook: Stephen Lower’s notes on Difference Between K and Q (HTML)
     
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    Instructions: Please read this section to gain a general understanding of the differences between the reaction quotient, Q, and the equilibrium constant, K.

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  • Reading: General Chemistry Virtual Textbook: Stephen Lower’s notes on Equilibrium Calculations Link: General Chemistry Virtual Textbook: Stephen Lower’s notes on Equilibrium Calculations (HTML)
     
    Also available in:
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    Instructions: Please read this section to gain a general understanding of how to use equilibrium constant expressions in calculations.  This section contains several examples of how to calculate equilibrium constants when concentrations are provided and how to calculate the concentration of one of the species in the reaction when equilibrium constants are provided.

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2.2 Solubility   2.2.1 Solutes and Solvents   Note: Remember to distinguish molarity from molality!  Solution chemistry nearly always uses molarity (measured in liters), while colligative properties will always use molality (measured in kilograms).  

2.2.2 Concentration Units   - Reading: Fordham Prep: Gregory L. Curran’s notes on Molarity Link: Fordham Prep: Gregory L. Curran’s notes on Molarity (HTML)
 
Instructions: Please read this section beginning with the title Molarityto gain a general understanding of how to calculate the molarity of a solution.  Note that molarity is the most common concentration unit used in solution chemistry.
 
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  • Reading: Clackamas Community College: Eden Francis’ notes on Molarity Link: Clackamas Community College: Eden Francis’ notes on Molarity(HTML)
     
    Instructions: Please read this section to gain a general understanding of how this concentration unit can be used in stoichiometric calculations.  
     
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  • Reading: Aus-e-Tute’s notes on Molality Link: Aus-e-Tute’s notes on Molality (HTML)
     
    Instructions: Please read this section to gain a general understanding of how to calculate the molality of a solution.  Note that molality and molarity are different and are not to be confused.

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  • Reading: Aus-e-Tute’s notes on Weight Percentage Link: Aus-e-Tute’s notes on Weight Percentage (HTML)
     
    Instructions: Please read this section to gain a general understanding of how to calculate the mass percent of solute in a solution.

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2.2.3 Periodic Rules of Solubility   Note: There are certain rules of solubility that you must commit to memory.  For example, you should memorize the fact that all nitrates and potassium compounds are soluble.  You should also know the insoluble products (like lead sulfate, calcium carbonate, and silver iodide) that most commonly show up in chemistry problems.  Remember those period rules!

  • Reading: Aus-e-Tute’s notes on Solubiliy Rules Link: Aus-e-Tute’s notes on Solubility Rules (HTML)
     
    Instructions: Please read this section beginning with the title Rules for Learning the Solubility of Ionic Compounds in Waterto gain a general understanding of the extent of solubility of compounds in water.  These solubility rules must be memorized.

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2.2.4 Solubility Equilibria (Ksp) and the Common Ion Effect   Note: Remember that the common ion is usually very soluble as part of one compound but insoluble as part of another.  This means that the common ion can never be an ion that is always soluble.

2.3 Colligative Properties   - Reading: Aus-e-Tute’s notes on Colligative Properties Link: Aus-e-Tute’s notes on Colligative Properties (HTML)

 Instructions: Please read this section to gain a general
understanding of colligative properties and their importance in
solution chemistry.  

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2.3.1 Freezing-Point Depression and Boiling Point Elevation   - Reading: Freezing-Point Depression and Boiling Point Elevation Link: Aus-e-Tute’s notes on Freezing Point Depression and Boiling Point Elevation (HTML)
 
Instructions: Please read this section to gain a general understanding of how to calculate the melting point and the freezing point of a given solution.  

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2.3.2 Raoult’s Law   - Reading: Aus-e-Tute’s notes on Raoult’s Law Link: Aus-e-Tute’s notes on Raoult’s Law (HTML)
 
Instructions: Please read this section to gain a general understanding of how to calculate vapor pressure of solutions.  

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2.3.3 Osmotic Pressure   Note: Colligative properties do not depend on the specific properties of the solute molecules in a given solution, but solely on the number of solute molecules that are in it.   This is one of the few rules in chemistry NOT determined by the specific characteristics of a solution!

  • Reading: Aus-e-Tute’s notes on Osmotic Pressure Link: Aus-e-Tute’s notes on Osmotic Pressure (HTML)
     
    Instructions: Please read this section to learn how to calculate the osmotic pressure of a solution using the van’t Hoff equation.  

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