Question 1Warm-upFoundation
A reaction gives off 60 cm³ of gas in 30 s. Calculate the mean rate.
Volume ÷ time.
Worked solution
- cm³/s
Answer: cm³/s
GCSE & IGCSE chemistry practice
Rate of reaction questions and answers
The mean rate of a reaction is the amount of reactant used, or product made, divided by the time: mean rate . It can be measured in g/s or cm³/s (and in mol/s at Higher). Rate increases with temperature, concentration, pressure, surface area and catalysts.
15 questions · Foundation and Higher tier · Every answer is checked as you type it, with a full worked solution. Updated .
Where rate of reaction comes up
| GCSE (AQA) | Chemistry and Combined Science, Foundation and Higher: calculate the mean rate of reaction (g/s or cm³/s). Higher only: rates in mol/s and the rate at a given time from the gradient of a tangent. |
|---|---|
| Cambridge IGCSE (0620) | Core: practical methods for investigating rate, such as change in mass or gas formed, and factors affecting rate. Supplement: explain the effects using collision theory and activation energy. |
The method
- Mean rate = change in quantity ÷ time taken.
- Use the change, not the final value, if the reading didn't start at zero.
- Units: g/s for mass, cm³/s for gas volume.
- Faster rate: a steeper graph, and the reaction finishes sooner.
Rate of reaction questions
Try each one before looking at the hint. If you're stuck, the AI tutor can talk you through it step by step.
Warm-up
Question 2Warm-upFoundation
A flask loses 1.2 g of mass in 40 s as gas escapes. Calculate the mean rate.
Mass ÷ time.
Worked solution
- g/s
Answer: g/s
Question 9Warm-upFoundation
A reaction gives off 75 cm³ of gas in 25 s. Calculate the mean rate.
Mean rate = amount of product ÷ time.
Worked solution
- cm³/s
Answer: cm³/s
Question 10Warm-upFoundation
A flask loses 0.9 g of mass in 60 s. Calculate the mean rate.
Mass lost ÷ time.
Worked solution
- g/s
Answer: g/s
Exam-style
Question 3Exam-styleFoundation
The gas volume is 15 cm³ at 10 s and 45 cm³ at 40 s. Calculate the mean rate between these times.
Use the change in volume and the change in time.
Worked solution
- cm³; s
- cm³/s
Answer: cm³/s
Question 4Exam-styleFoundation
A reaction produces 96 cm³ of gas in 2 minutes. Calculate the mean rate in cm³/s.
2 minutes = 120 s.
Worked solution
- cm³/s
Answer: cm³/s
Question 5Exam-styleFoundation
Reaction A makes 50 cm³ of gas in 25 s. Reaction B makes 80 cm³ in 50 s. Which is faster, and what is its mean rate?
Calculate both rates.
Worked solution
- A: cm³/s
- B: cm³/s, so A is faster
Answer: A, cm³/s (B is cm³/s)
Question 6Exam-styleFoundation
Why does increasing the temperature increase the rate of reaction?
Think about collision theory.
Worked solution
- Higher temperature: particles have more kinetic energy, collide more often, and a bigger proportion of collisions are successful.
Answer: Particles move faster: more frequent collisions, and more of them have at least the activation energy
Question 11Exam-styleFoundation
The volume of gas is 20 cm³ at 10 s and 50 cm³ at 30 s. Calculate the mean rate between these times.
Change in volume ÷ change in time.
Worked solution
- cm³/s
Answer: cm³/s
Question 12Exam-styleFoundation
A reaction produces 54 cm³ of gas in 3 minutes. Calculate the mean rate in cm³/s.
Convert minutes to seconds.
Worked solution
- min s
- cm³/s
Answer: cm³/s
Question 13Exam-styleFoundation
Why does powdered calcium carbonate react faster with acid than lumps of the same mass?
Think about how many particles the acid can reach.
Worked solution
- Powder exposes more particles to the acid, so there are more collisions per second.
Answer: Larger surface area, so more frequent collisions
Challenge
Question 7ChallengeHigher
0.02 mol of carbon dioxide is produced in 50 s. Calculate the mean rate in mol/s.
Moles ÷ time.
Worked solution
- mol/s
Answer: mol/s ( mol/s)
Question 8ChallengeHigher
A reaction makes 0.44 g of carbon dioxide in 20 s. Calculate the mean rate in mol/s. ( of CO₂ = 44)
Convert the mass to moles first.
Worked solution
- mol
- mol/s
Answer: mol/s
Question 14ChallengeHigher
0.24 g of magnesium reacts completely in 25 s. Calculate the mean rate of reaction in mol/s. (Mg = 24)
Convert mass to moles first.
Worked solution
- Moles mol
- mol/s
Answer: mol/s
Question 15ChallengeHigher
A reaction produces 240 cm³ of hydrogen at room temperature and pressure in 50 s. Calculate the mean rate in mol/s. (1 mol of gas occupies 24 dm³ at r.t.p.)
24 dm³ = 24 000 cm³.
Worked solution
- Moles mol
- mol/s
Answer: mol/s
Common mistakes
- Dividing time by quantity.
- Using the total reading when the start wasn't zero.
- Forgetting units.
Stuck on one of these?
The TutorAura AI tutor works through it with you step by step, with the reason for each step, then gives you one like it to try. It checks your working too.
Try the AI tutor freeMore chemistry questions
Sources
The questions are our own. The “where it comes up” notes are from each board's published specification, checked on 27 October 2026:
Practise chemistry with your own AI tutor
Questions at your level, help when you're stuck, and a plan for your exams. Free for 3 days, no card needed.