Equilibria · SHS3 Chemistry

Lesson notes

Learning Objectives

Indicator: 3.1.2.LI.1 - Explain hydration and hydrolysis of salts and predict the acidity or alkalinity of aqueous salt solutions.

By the end of the lesson, learners can:

Define hydration of salts and explain why it is an exothermic physical process involving the attraction between water molecules and ions in a crystal lattice.
Explain how the size and charge of an ion affect the enthalpy of hydration (hydration energy) of a salt.
Define hydrolysis of salts and use chemical equations to distinguish between cation hydrolysis and anion hydrolysis.
Predict whether an aqueous solution of a given salt will be acidic, basic or neutral by identifying which ion undergoes hydrolysis.
Explain why salts formed from strong acids and strong bases do not undergo hydrolysis and therefore give neutral solutions.

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Curriculum details

Strand: Physical Chemistry (Strand 1)
Sub-strand: Equilibria (1.2)
Content standard: 3.1.2.CS.2 - Demonstrate knowledge and understanding of concepts of hydration and hydrolysis of salt. 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.1 - Explain hydration and hydrolysis of salts and predict the acidity or alkalinity of aqueous salt solutions.
Suggested placement: Semester 1, Week 8 (Week 8 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. 97

Exemplars (from the NaCCA curriculum)

Talk for Learning: In mixed-ability groups, brainstorm to come out with the meaning of hydration
Collaborative Learning:
- Use chemical equations to illustrate hydration of salts.
- Explain some key features of hydration (exothermic in nature, a physical process).
- Discuss the factors that affect hydrated energy a. Size of ion b. Charge on the ion
Talk for Learning: Brainstorm to come out with the meaning of hydrolysis and discuss the types of hydrolysis (cation and anion hydrolysis).
Collaborative Learning:
- Use chemical equations to illustrate the mechanisms hydrolysis of salts (cation and anion).
- Explain why some salts do not undergo hydrolysis.
Teaching and Learning Materials:
- * Worksheets
Assessment (3.1.2.AS.1). The document marks these depth-of-knowledge levels for this indicator: Level 2 Skills of conceptual understanding.