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LeChatelier's Principle

LeChatelier's Principle

Author: carolyn fruin
Description:

Learning Targets:

  • I can define LeChatelier’s Principle.

  • I can state the STRESS caused by the following changes:
    Add/remove a reactant or product
    Increase/decrease volume
    Increase/decrease temperature
    Add a catalyst

  • I can predict how stresses on a system SHIFT the reaction’s equilibrium position.

  • I can determine how the amounts/concentrations of reactants and products change after the reaction shifts to restore equilibrium.

(more)
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Tutorial

LeChatelier's Notes

Notes: LeChatelier's Principle

Here is a set of examples using LeChatelier's Principle to predict the direction shift of a reaction when it is subjected to a stress.

Full Screen

LeChatelier's Principle

This video defines the term "stress" and describes what a system does to counteract stresses put upon it.

Source: KhanAcademy

Directions for the following videos:

View each of the demonstrations. Respond to the following questions:

Chromate-Dichromate Demo           2H+(aq) + 2CrO42–(aq) <----> Cr2O72–(aq) + H2O(ℓ)

What color is each side of the equilibrium? (be specific, this is important that you observe this)

 

How can we tell when this system reaches equilibrium?

 

When H+(aq) was added, the system shifted to the [ right | left ], changing from                to         

When OH(aq) was added, the system shifted to the [ right | left ], changing from               to         

 

NO2 Tubes Demo                              2 NO2(g) <----> N2O4(g) + heat

What color is each side of the equilibrium? (be specific, this is important that you observe this)

 

When the tubes were heated, the system shifted to the [ right | left ], changing from              to              

When the tubes were cooled, the system shifted to the [ right | left ], changing from            to          .

 

CoCl42– Solutions Demo                    Co2+(aq) + 4 Cl(aq) + heat <----> CoCl42–(aq)

What color is each side of the equilibrium? (be specific, this is important that you observe this)

 

When HCl(aq) was added, the system shifted to the [ right | left ], changing from               to                    .

When Ag+(aq) was added, the system shifted to the [ right | left ], changing from               to                  .

When the tubes were heated, the system shifted to the [ right | left ], changing from              to         

When the tubes were cooled, the system shifted to the [ right | left ], changing from             to                    .

Chromate - Dichromate Demo

This is a video of the chromate-dichromate equilibrium reaction with various stresses added.

Nitrogen dioxide Demonstration

Sealed tubes of nitrogen dioxide are exposed to various temperatures.

Cobalt Chloride Complex Ion Equilibrium

Different stresses are applied to one of the complex ions of cobalt and the system is observed over time..

Equilibrium Lab Investigation

Print the document below if you did not receive it in class. For each of the steps in the lab, find it in the video and record the results. You may need to rewind several times to be sure you have completed the data table. This lab will be completed in your lab book for class.

Iron Thiocyanate Equilibrium Reaction

Various stresses are applied to the complex ion equilibrium and the results can be seen here.