Equilibria · SHS2 Chemistry

Lesson notes

Learning Objectives

Indicator: 2.1.2.LI.1 - Explain Arrhenius, Bronsted-Lowry and Lewis concepts of acids and bases.

By the end of the lesson, learners can:

State the Arrhenius definition of acids and bases and identify the strengths and limitations of the theory using specific examples.
Explain the Bronsted-Lowry theory of acids and bases as proton donors and proton acceptors, and deduce conjugate acid-base pairs in given reactions.
Classify Bronsted-Lowry acids into simple acids, oxoacids and hydrated cations with appropriate examples of each.
Apply the Lewis theory to define acids as electron-pair acceptors and bases as electron-pair donors, and evaluate its advantages over the earlier theories.
Compare the three acid-base concepts and justify which theory best explains a given chemical reaction, including reactions that do not involve hydrogen ions.

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Curriculum details

Strand: Physical Chemistry (Strand 1)
Sub-strand: Equilibria (1.2)
Content standard: 2.1.2.CS.2 - Demonstrate knowledge and understanding of the concepts and properties of acids and bases to classify substances as well as determine concentration of analysis through titration. 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.1 - Explain Arrhenius, Bronsted-Lowry and Lewis concepts of acids and bases.
Suggested placement: Semester 1, Week 17 (Week 17 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. 71

Exemplars (from the NaCCA curriculum)

Collaborative Learning: With the aid of charts or videos, brainstorm to find answers to the following tasks:
- Arrhenius theory of acids and bases and give their strengths and limitations
- Bronsted-Lowry theory of acids and bases and give their strengths and limitations.
- Types of Bronsted-Lowry acids (simple acids, oxoacids and hydrated cations) and bases.
- Lewis theory of Acids and Bases and give their strengths and limitations.
Activity-Based Learning:
- Deduce the conjugate acid-base pairs in a given acid-base reaction.
- Classify household chemical, fruits, vegetables etc as acids or bases
- Watch video to reinforce the concepts.
Teaching and Learning Materials:
- * Worksheets with illustrative examples of Arrhenius,
- Bronsted-Lowry and Lewis acids and bases for
- Learners to identify * Fruits * Vegetables * Common acids (HCl, HNO , H SO CH COOH,
- H CO , 2 3 * Bases * Universal indicator with pH colour chart * Litmus papers * Ammonium compound (e.g., ammonium chloride) * Bases: NaOH(aq), KOH(aq), Ca(OH) , NH * Zinc chips, iron filings, magnesium ribbon * pH meter * A simple electric circuit with electric bulb/ lamp, beakers, wire, key/switch
- 3 2 4, 3
- 2 3
- * Mixture of Na CO and * Methyl orange and phenolphthalein
- Burette * Pipette * Conical flask * Droppers * Retort stand and clamp * Pipette filler * White tile * Wash bottle with distilled * Calculator
- NaHCO ) 2 3 3 indicators
- water
Assessment (2.1.2.AS.1). The document marks these depth-of-knowledge levels for this indicator: Level 3 Strategic reasoning.