Chemistry Year 11 - Module 4 - Lesson 13
⚖️ Gibbs Free Energy & Spontaneity
1. Key Ideas
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- Key facts and terms for ⚖️ Gibbs Free Energy & Spontaneity
- How the main ideas in ⚖️ Gibbs Free Energy & Spontaneity connect
2. Success Criteria
By the end, you should be able to:
- Key facts and terms for ⚖️ Gibbs Free Energy & Spontaneity
- Where this lesson fits in Module 4
- How the main ideas in ⚖️ Gibbs Free Energy & Spontaneity connect
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. Q6 (6 marks) Explain, using the equation $\Delta G = \Delta H - T\Delta S$, why the decomposition of calcium carbonate ($\text{CaCO}_3 \to \text{CaO} + \text{CO}_2$) is non-spontaneous at room temperature but spontaneous in a lime kiln at 900°C. In your answer, identify the ΔH/ΔS combination category and calculate the crossover temperature.
2. Q7 (6 marks) The rusting of iron: $4\text{Fe(s)} + 3\text{O}_2\text{(g)} \to 2\text{Fe}_2\text{O}_3\text{(s)}$ has $\Delta H° = -1648 \text{ kJ mol}^{-1}$ and $\Delta S° = -549 \text{ J K}^{-1}\text{mol}^{-1}$. (a) Calculate ΔG° at 25°C. (b) Is rusting spontaneous? (c) Calculate T cross . (d) Rusting is slow at room temperature. Distinguish between the thermodynamic and kinetic aspects of this observation.
3. Q8 (8 marks) Evaluate the statement: "The Haber process is run at 400–500°C because the reaction is thermodynamically spontaneous at high temperatures." Is this statement correct? In your answer, calculate ΔG° at both 25°C and 450°C, explain the concept of T cross , and distinguish between thermodynamic and kinetic factors. Use: $\Delta H° = -92.4 \text{ kJ mol}^{-1}$; $\Delta S° = -198.9 \text{ J K}^{-1}\text{mol}^{-1}$.
6. Extend: Apply the Idea
A student gives a memorised answer about ⚖️ Gibbs Free Energy & Spontaneity 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 ⚖️ Gibbs Free Energy & Spontaneity?
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 ⚖️ Gibbs Free Energy & Spontaneity?
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.