Chemistry Year 12 - Module 6 - Lesson 5
Strong vs Weak Acids & Bases — The Critical Distinction
1. Key Ideas
The single most consequential distinction in Module 6 is not between acids and bases — it is between strong and weak acids, and confusing the two leads to wrong arrow notation, wrong pH calculations, and wrong indicator selection every time.
- The six strong acids: HCl, H₂SO₄ (1st), HNO₃, HClO₄, HBr, HI
- Strength = degree of ionisation (Ka) — intrinsic, temperature-dependent, not concentration-dependent
2. Success Criteria
By the end, you should be able to:
- The six strong acids: HCl, H₂SO₄ (1st), HNO₃, HClO₄, HBr, HI
- The four strong bases: NaOH, KOH, Ca(OH)₂, Ba(OH)₂
- All other acids and bases encountered in HSC are weak
3. Key Terms
4. Activity: Build the Lesson Map
Use the lesson to complete the table. Keep answers brief but specific.
| Prompt | Your answer |
|---|---|
| Main concept | |
| Important example | |
| Common mistake to avoid | |
| How this links to the next lesson |
5. Short Answer Questions
1. Explain this lesson goal in your own words: "The six strong acids: HCl, H₂SO₄ (1st), HNO₃, HClO₄, HBr, HI". Use one specific example from the lesson.
2. Apply this idea to a new example: "The four strong bases: NaOH, KOH, Ca(OH)₂, Ba(OH)₂". Show your reasoning clearly.
3. Analyse why this idea matters for understanding Strong vs Weak Acids & Bases — The Critical Distinction: "All other acids and bases encountered in HSC are weak".
6. Extend: Apply the Idea
A student gives a memorised answer about Strong vs Weak Acids & Bases — The Critical Distinction but does not use evidence or reasoning.
Improve the answer by writing a stronger response that uses accurate terminology, a relevant example and a clear explanation.
7. Multiple Choice
1. What is the best first step when answering a question about Strong vs Weak Acids & Bases — The Critical Distinction?
A. Identify the key concept being tested
B. Write every fact from memory
C. Ignore the command word
D. Skip examples and evidence
2. Which answer would show stronger understanding of Strong vs Weak Acids & Bases — The Critical Distinction?
A. An answer with accurate terms and reasoning
B. A copied definition only
C. A single-word response
D. An answer with no example
3. What should you do if a question asks you to explain?
A. Link the idea to a reason or cause
B. List unrelated facts
C. Only draw a diagram
D. Write the shortest possible answer
8. Success Criteria Proof
Finish with evidence that you can do each success criterion.