SOLUBILITY, EQUILIBRIUM, AND FORMING PRECIPITATES
What is a Solubility Product?
A solubility product refers to nothing more than an equilibrium constant for a special case of equilibrium where there is excess solute in equilibrium with its aqueous solution. In other words, it is the K value for a system in dynamic equilibrium in which there is solid material along with dissolved ions in solution.
A solubility product refers to nothing more than an equilibrium constant for a special case of equilibrium where there is excess solute in equilibrium with its aqueous solution. In other words, it is the K value for a system in dynamic equilibrium in which there is solid material along with dissolved ions in solution.
LESSON OVERVIEW (SPECIFIC EXPECTATIONS: E2.3, E2.4, E3.3)
Lesson Hook:
Both Cornell University and a young man by the name of Neil Wacaster have created "solubility songs" based off the solubility table. A neat lesson hook would be to introduce the topic of solubility using these songs, and they may also appeal to multiple intelligence's! Click below for both versions of the "Solubility song"
Both Cornell University and a young man by the name of Neil Wacaster have created "solubility songs" based off the solubility table. A neat lesson hook would be to introduce the topic of solubility using these songs, and they may also appeal to multiple intelligence's! Click below for both versions of the "Solubility song"
Action:
Given the fact that this topic is nothing more than a special case of equilibrium, it is quite easy to cover the material using an inquiry based approach by having students preform a lab on solubility and calculating solubility product constants. Students can observe the formation of precipitates and predict whether or not precipitates will form for a variety of systems and are quite capable of preforming the calculations required once they understand the relationship between Q, the reaction quotient, and predicting precipitation. This could be introduced either before the lab or after for a more inquiry based approach along with the solubility table provided in most high school textbooks. Click below for a complete lab of determining the Ksp value for calcium hydroxide courtesy of The University of Toronto-OISE.
Given the fact that this topic is nothing more than a special case of equilibrium, it is quite easy to cover the material using an inquiry based approach by having students preform a lab on solubility and calculating solubility product constants. Students can observe the formation of precipitates and predict whether or not precipitates will form for a variety of systems and are quite capable of preforming the calculations required once they understand the relationship between Q, the reaction quotient, and predicting precipitation. This could be introduced either before the lab or after for a more inquiry based approach along with the solubility table provided in most high school textbooks. Click below for a complete lab of determining the Ksp value for calcium hydroxide courtesy of The University of Toronto-OISE.
This is a pre-lab for determining the Ksp value for calcium hydroxide courtesy of the Ontario Institute for Studies in Education, University of Toronto. Click the file below to download this word document.
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This is a relatively straightforward lab to determine the Ksp value for calcium hydroxide complete with calculations, discussion questions and lab rubric courtesy of the Ontario Institute for Studies in Education, University of Toronto. Click the file below to download this word document.
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This is the answer key for the lab calculations and discussion questions courtesy of the Ontario Institute for Studies in Education, University of Toronto. Click the file below to download this word document.
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This is an entire lesson plan for the calcium hydroxide Ksp lab including specific expectations and possible lesson hooks courtesy of the Ontario Institute for Studies in Education, University of Toronto. Click the file below to download this word document.
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In addition to preforming a lab, students can also "view" the addition of salts in solution using a computer simulation courtesy of The university of Colorado Phet. This simulation allows students to "see" the solution on a molecular level while dissolving salts and creating precipitates They are also able to view the exchange between ions in solution and the precipitate or solid species. Please click below to download this simulation by Phet entitled Soluble Salts.
Soluble Salts | |
File Size: | 1624 kb |
File Type: | jar |
Misconceptions Addressed: Students think that if you add more solid, the equilibrium concentration of aqueous species will increase.
Debrief:
This lab may take all class to complete, with the calculations and discussion questions to be left for homework so it is a good idea to take 5-10 minutes at the end of class to go through the results found and preform a sample calculation for the students such that they have something to work off of while completing the lab.
FOPP: Commitment to students and student learning, professional knowledge and ongoing professional learning.
Debrief:
This lab may take all class to complete, with the calculations and discussion questions to be left for homework so it is a good idea to take 5-10 minutes at the end of class to go through the results found and preform a sample calculation for the students such that they have something to work off of while completing the lab.
FOPP: Commitment to students and student learning, professional knowledge and ongoing professional learning.
The concept of solubility and forming precipitates can be reinforced in a variety of ways to appeal to all forms of multiple intellegences. Click below for a few resources that can be used in conjunction with a lesson to further demonstrate this concepts.