Kinetics I
Notes for every section, eight new exam-style questions with full worked solutions, and online recall cards for your review days. Nothing here is copied from the book.
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9.1 Rate of reaction and collision theory
Rate of reaction: the change in concentration (or amount) of a reactant or product per unit time.
Collision theory: for particles to react they must collide with the correct orientation and with energy at least equal to the activation energy. Most collisions do not lead to a reaction.
Anything that increases the number of successful collisions per second increases the rate. It is the frequency of successful collisions that matters, not just the total number.
Check yourself: State the two conditions for a collision to be successful.
Correct orientation and energy at least equal to the activation energy
9.2 The factors that change the rate
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9.3 Measuring rates of reaction
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9.4 Rates from graphs: drawing tangents
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9.5 The Maxwell–Boltzmann distribution
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9.6 How temperature changes the rate
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9.7 Catalysts and reaction profiles
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9.8 Catalysts and the Maxwell–Boltzmann distribution
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9.9 Heterogeneous catalysts in industry
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9.10 The economic benefits of catalysts
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Extra worked questions
Cover the solution, answer on paper, then mark yourself against each step. Each step shows the mark it earns.
All 8 worked solutions are free for members. The first one is open to everyone.
A mean rate
In the first 2.0 minutes of a reaction, 48 cm3 of hydrogen is collected. Calculate the mean rate in cm3 s−1.
Try it first, then show the worked solution
| Time in seconds | 2.0 min = 120 s | 1 |
|---|---|---|
| Rate | 48 ÷ 120 = 0.40 cm3 s−1 | 1 |
Answer: 0.40 cm3 s−1
Examiner tip: Check which time unit the question wants before you divide.
Concentration and rate
Use collision theory to explain why magnesium reacts faster with 2.0 mol dm−3 hydrochloric acid than with 0.5 mol dm−3 acid.
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Rate from a tangent
A tangent drawn to a graph of gas volume against time at t = 30 s passes through (0 s, 12 cm3) and (80 s, 52 cm3). Calculate the rate at 30 s.
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Features of the distribution
Give three features of the Maxwell–Boltzmann distribution for a gas at a fixed temperature.
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A small temperature rise
Explain, using the Maxwell–Boltzmann distribution, why a small rise in temperature causes a large increase in the rate of a reaction.
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A catalyst on the distribution
Explain, with reference to the Maxwell–Boltzmann distribution, how a catalyst increases the rate of a reaction.
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Thiosulfate at two temperatures
In the thiosulfate practical, the cross disappears after 80 s at 20 °C and after 38 s at 30 °C. (a) Calculate 1/t for each. (b) By what factor has the rate increased? (c) Give one way to make the temperature measurement more valid.
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How a solid catalyst works
Platinum in a catalytic converter helps convert CO and NO into CO2 and N2. Describe how a heterogeneous catalyst works, explain why it is coated onto a ceramic honeycomb, and explain why leaded petrol must not be used.
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Video walkthroughs
Narrated walkthroughs of exam-style questions from this topic of the book, showing where each mark comes from. Try the question first, then watch. Captions are available in the player.
Collision theory: pressure and rate
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Reaction profile with a catalyst
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Rates from tangents
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How a catalytic converter works
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The disappearing cross: one over time
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Recall cards
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Your review days
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- +3 Recall cards and Q1 to Q4
- +7 Recall cards and Q5 to Q8
- +14 Recall cards and Q9 to Q12
- +30 Full chapter test, timed
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