Equilibria · SHS3 Chemistry

Lesson notes

Learning Objectives

Indicator: 3.1.2.LI.2 - Explain the terms oxidizing agent, reducing agent, redox half equations and apply the principles in redox titrations.

By the end of the lesson, learners can:

Define oxidizing agent and reducing agent using the three definitions of oxidation and reduction (electron transfer, oxidation number change, and addition/removal of oxygen or hydrogen).
Identify the oxidizing agent and reducing agent in a given redox reaction by calculating changes in oxidation numbers of the species involved.
Deduce balanced half-equations for oxidation and reduction processes given the species involved, and combine them to write an overall redox equation.
Explain the steps for balancing redox equations in acidic and basic media using the ion-electron (half-equation) method.
Apply the principles of redox reactions to perform calculations involving redox titrations, specifically determining the concentration of an analyte from titration data.

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Curriculum details

Strand: Physical Chemistry (Strand 1)
Sub-strand: Equilibria (1.2)
Content standard: 3.1.2.CS.4 - Demonstrate knowledge and understanding of redox and apply its principles to electrochemical cells as well as their importance in everyday life. 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.2 - Explain the terms oxidizing agent, reducing agent, redox half equations and apply the principles in redox titrations.
Suggested placement: Semester 1, Week 14 (Week 14 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. 99

Exemplars (from the NaCCA curriculum)

Initiating Talk for Learning:
- Using think-pair-share approach, discuss the meaning of oxidizing and reducing agents in terms of the three definitions of oxidation and reduction reactions.
- Identify oxidizing and reducing agents from oxidation and reduction reactions based on changes in oxidation number of species involved.
- Deduce simple oxidation and reduction half-equations given species involved in oxidation and reduction reactions and vice versa.
- Explain the steps involved in balancing oxidation and reduction equations using medium method (in acidic and basic media).
Inquiry-Based Learning: In small mixed-ability groups, design and perform oxidation and reduction titrations involving:
- KMnO versus Fe 2+ 4
- KMnO versus C O 4 2 42-
- I /KI versus S O 32- 2 2
Problem Solving Approach: Calculate the concentration of an analyte, analyse and interpret the results.
Exploratory Learning: Perform experiment to qualitatively test for the presence of oxidizing agents and reducing agents.
Talk for Learning: Use charts, pictures, videos, to discuss the application of oxidizing and reducing agents in:
- Beautician industry
- Motor traffic control
- Catalytic converter
- Extraction of iron using carbon (II) oxide as reducing agent.
- Household and swimming pool disinfection.
Teaching and Learning Materials:
- * Test tubes in a rack * Strips of copper foil * Strips of zinc foil * * 0.1M potassium bromide
- Strip of silver wire * * ICT tools Emery paper * * Calculator 0.5 M copper sulphate solution * 0.5 M zinc sulphate solution
- * 0.1 M silver nitrate solution * 50 ml Burettes * 25 ml pipettes * 250 ml conical flasks * 100 ml beakers * White tiles
- * Retort stands * solution
- KMnO 4 * * 0.02M potassium Iron (II) solution * manganate (VII) Iodine solution * Potassium iodide * Na S O 2 2 3 * Starch * * Electrolysis cell Test tubes * Test tube rack
- * Copper powder * Zinc powder * * Clamps and stands Bromine water * * Cover slides 0.1 M potassium iodide solution * 0.1 M potassium chloride solution
- * 0.1 M Iron (III) chloride
- * Power pack
- * Connecting wires and clips
- * Wooden splint * Droppers * 1 M tetraoxosulphate (VI) acid * 1 M sodium chloride solution
- * 1 M copper(II) chloride * Identical fresh nails * Test tube in test tube racks * Stoppers * Spatula * PH sensor * Temperature sensor * Stands and clamps
- * Calcium chloride * Oil * Iron coated with zinc * Iron coated with tin * Iron filings * Salt
Assessment (3.1.2.AS.2). The document marks these depth-of-knowledge levels for this indicator: Level 4 Extended critical thinking and reasoning.