AQA GCSE Chemistry (8462), Higher tier · The rate and extent of chemical change › Rate of reaction
Practise Calculating rates of reactions. 17 exam-style questions plus unlimited generated ones on this subtopic, at up to four difficulty levels, with full mark schemes and a progress tracker. Free, no account needed.
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A reaction produces 45 cm3 of gas in 30 s. Calculate the mean rate of reaction.
1.5 cm3/s
Sample questions
Written for this site in the style of AQA exam questions. They are not taken from real past papers.
Question 1Easy4 marks
The mean rate of a reaction can be calculated using: mean rate of reaction = quantity of reactant used or product formed ÷ time taken
(a) A reaction produces 45 cm3 of gas in 30 s. Calculate the mean rate of reaction.[1]
(b) In a different reaction, carbon dioxide is produced at a mean rate of 0.015 g/s. Calculate the mass of carbon dioxide produced in 120 s.[2]
(c) Which of these is a correct unit for the rate of a reaction? Tick (✓) one box.[1]
cm3
cm3/s
s/cm3
s
Show the answer and mark scheme
(a)Answer: 1.5 cm3/s
1.5 (cm3/s)
(b)Answer: 1.8 g
0.015 × 120
1.8 (g)
(c)Answer: cm3/s
Question 2Medium5 marks
A student added excess calcium carbonate powder to 50 cm3 of dilute nitric acid in a flask on a balance, and recorded the total mass at intervals. The mass of the flask and contents was 184.62 g at the start and 183.86 g after the reaction had finished.
(a) Explain why the mass decreased during the reaction.[1]
(b) The reaction took 240 s to finish. Calculate the mean rate of reaction over this time. Give your answer to 2 significant figures.[3]
(c) Suggest how the student could tell, without waiting and weighing, that carbon dioxide gas was still being produced.[1]
Show the answer and mark scheme
(a)Answer: Carbon dioxide gas was produced and escaped from the open flask.
carbon dioxide gas is produced and escapes from the (open) flask
(b)Answer: 0.0032 g/s
184.62 − 183.86 = 0.76 (g)
0.76 ÷ 240
0.0032 (g/s)
(c)Answer: Bubbles (effervescence) would still be seen in the flask.
bubbles / fizzing (effervescence) can still be seen in the flask
Question 3Hard7 marks
Zinc reacts with dilute sulfuric acid. Zn(s) + H2SO4(aq) → ZnSO4(aq) + H2(g) In an experiment, 1.30 g of zinc reacted completely in 400 s.
(a) Calculate the mean rate of reaction in g/s. Give your answer in standard form.[2]
(b) Calculate the mean rate of reaction in mol/s. Relative atomic mass (Ar): Zn = 65[2]
(c) Calculate the mean rate at which hydrogen gas was produced, in cm3/s. The volume of one mole of any gas at room temperature and pressure is 24 dm3.[3]