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SHS2 Chemistry · Semester 1, Week 13

Equilibria

Lesson notes

Learning Objectives

Indicator: 2.1.2.LI.2 - State Le Chatelier’s Principle and apply it to deduce qualitatively, the effects of various factors on the positions of equilibrium and on the value of the equilibrium constant.

By the end of the lesson, learners can:

  1. State Le Chatelier’s Principle in their own words and explain what is meant by a “stress” on a system at equilibrium.
  2. Predict qualitatively the direction in which an equilibrium system will shift when the concentration of a reactant or product is changed, and explain why the value of Kc remains unchanged.
  3. Predict qualitatively the direction of shift when the temperature of a system is changed, and state whether Kc increases or decreases for exothermic and endothermic reactions.
  4. Predict the effect of changes in pressure and volume on systems involving gases, and explain why pressure changes have no effect on systems with equal numbers of gas molecules on both sides.
  5. Explain why a catalyst does not change the position of equilibrium nor the value of Kc, but only helps the system reach equilibrium faster.

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Curriculum details

Strand
Physical Chemistry (Strand 1)
Sub-strand
Equilibria (1.2)
Content standard
2.1.2.CS.1 - Demonstrate understanding that a balance of opposing reactions occur in chemical equilibrium systems to attain equilibrium and this principle is applied in chemical industrial processes. 2.1.2.LO.1 Explain that dynamic equilibrium is attained when the rates of the forward and backward reactions are equal and this principle has industrial applications. 2.1.2.LO.2 Apply your knowledge in acids and bases to classify and describe substances as acids and bases as well as determine the concentration of analyte through titration.
Indicator
2.1.2.LI.2 - State Le Chatelier's Principle and apply it to deduce qualitatively, the effects of various factors on the positions of equilibrium and on the value of the equilibrium constant.
Suggested placement
Semester 1, Week 13 (Week 13 of the year)

Our suggestion, laid out in curriculum order across three terms of twelve weeks. NaCCA does not fix the week, so follow your school's scheme of learning.

Curriculum reference
NaCCA curriculum document, p. 69

Exemplars (from the NaCCA curriculum) 

Talk for Learning Approach:
- Identify the factors that affect chemical equilibrium and use Le Chatelier's principle to predict the direction of the shifting from various possible stress (these should include changes in concentration, temperature, pressure, volume and catalyst) on a system at equilibrium
- In groups discuss and predict the effect of each of the factors on the position of equilibrium as well as the equilibrium constant.
Activity-Based Learning: Individually, identify and write down a set of conditions that will optimize a desired outcome of a reaction, such as a product.
Teaching and Learning Materials:
- * Video on the topic. * Worksheet containing tables to be completed on the equilibrium factors. * Worksheet with scaffolding strategies in Kc, Kp and Ksp
- CHARTS * Chart of the production line processes. * Chart of processes that are
- of the Haber and Contact
- reversible
Assessment (2.1.2.AS.2). The document marks these depth-of-knowledge levels for this indicator: Level 4 Extended critical thinking and reasoning.
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