amazon.co.ukKinetics and Equilibria
A-Level Chemistry revision: Kinetics and Equilibria. Learning objectives, key points, worked examples and practice questions across AQA, Edexcel, OCR, WJEC and CCEA.
๐ Key Points
Key Fact: Rate = Delta[conc]/Deltat; collision theory: effective collisions need E >= Ea and correct orientation
Key Fact: Maxwell-Boltzmann: at higher T, more molecules exceed Ea -> exponentially more effective collisions
Key Fact: Rate law: rate = k[A]แต[B]โฟ; m,n = order (not necessarily stoichiometric); overall order = m+n
Key Fact: 1st order: rate = k[A]; tยฝ = ln2/k (constant); ln[A] = -kt + ln[A]โ
Key Fact: Arrhenius: ln k = -Ea/RT + ln A; plot ln k vs 1/T gives slope -Ea/R
Key Fact: Le Chatelier: system shifts to oppose change. Conc: shift to consume added; Pressure: shift to fewer gas moles; Temp: exo shifts left on heating
Key Fact: Kc = [products]/[reactants] (equilibrium conc, powers = coeffs); Kp uses partial pressures
Key Fact: Kp = Kc(RT)^Deltan where Deltan = moles gas products - moles gas reactants
Key Fact: Catalyst: lowers Ea, increases rate equally both directions; NO effect on K or equilibrium position
๐ฏ Learning Objectives
- Explain collision theory and factors affecting rate: concentration, temperature, catalyst, surface area
- Use Maxwell-Boltzmann distribution to explain temperature effect
- Derive and use rate equations: rate = k[A]แต[B]โฟ; determine order experimentally
- Calculate rate constant k and half-life for 1st order reactions
- Understand activation energy and Arrhenius equation: k = Ae^(-Ea/RT)
- Apply Le Chatelier's principle to changes in concentration, pressure, temperature
- Write Kc and Kp expressions; relate Kp = Kc(RT)^(Deltan)
- Understand effect of catalysts on rate and equilibrium position
๐ก Worked Example
Exam-Style Question
Question: For Nโ + 3Hโ โ 2NHโ, DeltaH = -92 kJ/mol. Predict effect on yield of: (a) increasing pressure, (b) increasing temperature, (c) adding Fe catalyst
Model Answer:
(a) 4 mol gas -> 2 mol gas: shift right -> higher yield. (b) Exothermic: heating shifts left -> lower yield. (c) Catalyst speeds up both forward/reverse equally -> no effect on yield, reaches equilibrium faster
โ Practice Questions
Model answers are being added progressively - questions marked ✗ don't have one yet. Cross-check with your teacher or the official mark scheme.
Questions:
- Rate = k[A][B]^2. If [A] doubled and [B] tripled, rate factor?✗ answer coming soon
- Half-life of 1st order reaction is 10 min. k = ?✗ answer coming soon
- For 2SOโ + Oโ โ 2SOโ, write Kp. If P_total doubled, effect on yield?✗ answer coming soon
- Why does increasing temperature increase rate constant?✗ answer coming soon
- Explain why catalyst doesn't change equilibrium constant✗ answer coming soon
๐ฌ Video Resources
- Kinetics and Equilibria - Overview -- YouTube Search
- Kinetics and Equilibria - Exam Questions -- YouTube Search
๐ Past Papers & Exam Resources
๐ Further Reading & Resources
- Physics & Maths Tutor - Kinetics and Equilibria -- Free notes, worksheets, and past paper questions by topic
- Dr Frost Maths - Kinetics and Equilibria -- Free resources, slides, and interactive questions
- BBC Bitesize - Kinetics and Equilibria -- BBC Bitesize revision resources