SHS3 Chemistry · Semester 1 Week 3: Equilibria

Lesson notes

Learning Objectives

Indicator: 3.1.2.LI.3

By the end of the lesson, learners can:

Define a buffer solution and distinguish between acidic and basic buffer solutions, giving the composition of each.
Explain buffer action using the common ion effect and Le Chatelier’s principle to describe how a buffer resists pH change on addition of small amounts of acid or base.
Apply the Henderson-Hasselbalch equation to calculate the pH of a buffer solution given the concentrations of the weak acid and its salt (or weak base and its salt) and the Ka or Kb value.
Calculate the concentration of an unknown component of a buffer solution when the pH and other component concentrations are given.
Describe at least three real-life applications of buffer solutions in living systems and industries, explaining the role of the buffer in each case.

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Curriculum details

Strand: Physical Chemistry (Strand 1)
Sub-strand: Equilibria (1.2)
Content standard: 3.1.2.CS.1 - Demonstrate knowledge and understanding of the pH scale in determining the acidity and alkalinity of strong and weak acids, bases and aqueous solutions. 3.1.2.LO.1 Use the knowledge in pH to distinguish between solutions that are acidic, neutral or basic. 5 Gender Equality and Social Inclusion 6 Socio-Emotional Learning 3.1.2.LO.2 Use your knowledge and understanding of concepts in hydration and hydrolysis to determine the types of salts. 3.1.2.LO.3 Use the understanding of hydrolysis of salts to decide on suitable indicator as well as plot and interpret titration curves. 3.1.2.LO.4 Describe oxidation and reduction reactions and apply their principles to electrochemical cells as well as their importance in everyday life.
Indicator: 3.1.2.LI.3 - Explain buffer solution, buffer action and their applications in everyday life.
Suggested placement: Semester 1, Week 3 (Week 3 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. 96

Exemplars (from the NaCCA curriculum)

Collaborative Learning: In mixed-gender groups, research and give class presentations on: a. Buffer solution, its composition and how it behaves. b. How to calculate the pH of a buffer solution and the concentration of the various component of the buffer.
Experiential Learning: In mixed ability group, prepare a buffer solution of a specific pH, given a weak acid and its salt and weak base and its salt.
Inquiry-Based Learning: Give specific examples of the application of buffer in everyday life in: a. Living systems b. Industries
Teaching and Learning Materials:
- * pH scale * pH meter
- * Universal indicator * Calculator
Assessment (3.1.2.AS.3). The document marks these depth-of-knowledge levels for this indicator: Level 4 Extended critical thinking and reasoning.