Applications of Le Châtelier’s Principle

Product Details

What happens when the equilibrium is disturbed? Students investigate six chemical equilibrium systems to analyze patterns and trends in the principles, concepts and definitions of equilibrium.

Students begin with an activity that introduces the properties of a system at equilibrium: the reversible complex-ion reaction between iron(III) nitrate and potassium thiocyanate. Deliberate “stresses” are added to the system and students analyze the resulting color changes. This procedure provides a model for guided-inquiry analysis of five additional equilibrium systems. Inquiry activities include a reversible acid–base indicator reaction, copper and cobalt complex ions, gas–liquid solubility of carbon dioxide and the solubility of magnesium hydroxide. For convenience, these systems may be set up as lab stations.  

Complete for 24 students working in pairs. Refill kit includes chemicals and consumable supplies.

2024 CED Alignment:  

Unit 7 - Equilibrium 

Topic 7.9 - Introduction to LeChatelier's Principle 

Description of the Lab 

Students investigate how an equilibrium system responds to various stresses, including changes in concentration, temperature, and pressure. By observing visible color shifts in an iron thiocyanate equilibrium, students apply Le Châtelier’s Principle to explain the system’s behavior. 

Learning Objective 

• LO 7.9.A – Identify the response of a system at equilibrium to an external stress, using Le Châtelier’s principle. 

Skills Students Will Learn 

• 1.B – Describe the components of and quantitative information from models and representations that illustrate both particulate-level and macroscopic-level properties. 
  In this lab: Students connect observable color shifts to molecular models of equilibrium position. 

• 2.D – Make observations or collect data from representations of laboratory setups or results, while attending to precision where appropriate. 
  In this lab: Students document qualitative changes and determine how each stress affects equilibrium. 

• 6.E – Provide reasoning to justify a claim using connections between particulate and macroscopic scales or levels. 
  In this lab: Students use molecular reasoning to explain why the system shifts in response to each stressor.