Eduqas A Level Chemistry
Eduqas A Level Chemistry PI4.2 Entropy and Feasibility of Reactions Exam Questions
Free Eduqas A Level Chemistry exam questions on PI4.2 Entropy and Feasibility of Reactions, with mark schemes. Covers entropy, Gibbs free energy and feasibility.
PI4.2 Entropy and Feasibility of Reactions exam questions
1 question pack of real past exam questions with its mark scheme. Answer every question without notes, then mark your answers line by line against the mark scheme.
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A Level Chemistry Flashcards
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About Eduqas A Level Chemistry PI4.2 Entropy and Feasibility of Reactions
This topic explains why reactions happen.
What you need to know
- Entropy A measure of disorder; gases have higher entropy than liquids and solids.
- Entropy change ΔS = ΣS(products) − ΣS(reactants).
- Gibbs free energy ΔG = ΔH − TΔS; a reaction is feasible when ΔG ≤ 0.
- Temperature Find the temperature at which a reaction becomes feasible.
Common mistakes in PI4.2 Entropy and Feasibility of Reactions
- Forgetting to convert ΔS from J to kJ.
- Saying feasible reactions always occur quickly.
- Getting the sign of ΔS wrong for gas production.
Try three PI4.2 Entropy and Feasibility of Reactions exam-style questions
1. Calculate ΔG at 298 K if ΔH = +50 kJ mol⁻¹ and ΔS = +200 J K⁻¹ mol⁻¹. (2 marks)
Show the mark scheme answer
ΔG = 50 − 298 x 0.200 (1) = −9.6 kJ mol⁻¹ (1).
2. Explain why ΔS is positive for CaCO₃ → CaO + CO₂. (1 mark)
Show the mark scheme answer
A gas is formed from a solid, increasing disorder.
3. State the condition for feasibility. (1 mark)
Show the mark scheme answer
ΔG ≤ 0.
PI4.2 Entropy and Feasibility of Reactions FAQs
What does Entropy and Feasibility cover?
Entropy, Gibbs free energy and predicting feasibility.
What units are used?
ΔH in kJ mol⁻¹, ΔS in J K⁻¹ mol⁻¹, so convert before combining.
Can kinetics stop a feasible reaction?
Yes, if the activation energy is high.
Revise this topic with flashcards: A Level Chemistry Flashcards, with mark scheme answers for Anki and Quizlet.
