AQA GCSE Chemistry (8462), Higher tier · The rate and extent of chemical change › Rate of reaction
Practise Factors which affect the rate of reaction. 19 exam-style questions on this subtopic, at up to four difficulty levels, with full mark schemes and a progress tracker. Free, no account needed.
Required practical:Rates of reaction (method, variables and exam tips)
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Two students investigated how the concentration of sodium thiosulfate solution affects the time for a black cross to disappear, viewed through the solution from above.
Student A repeated the experiment three times with 40 g/dm3 solution and got times of 21 s, 22 s and 21 s.
Student B, using a different batch of the same concentration of sodium thiosulfate solution and a different stopwatch, got a time of 23 s.
What is meant by a result being reproducible?
A different person, or different equipment, gets very similar results.
Complete the word equation for the reaction. calcium carbonate + hydrochloric acid → calcium chloride + water + ______________
carbon dioxide
Sample questions
Written for this site in the style of AQA exam questions. They are not taken from real past papers.
Question 1Easy5 marks
Marble chips react with dilute hydrochloric acid.
(a) Which two changes would increase the rate of the reaction? Tick (✓) two boxes.[2]
Use larger marble chips
Use powdered marble
Use more dilute acid
Increase the temperature
Use a bigger flask
(b) Give one other factor that affects the rate of a chemical reaction.[1]
(c) A student says: 'Using powdered marble instead of the same mass of marble chips will produce more carbon dioxide.' Is the student correct? Explain your answer.[2]
Show the answer and mark scheme
(a)Answer: Use powdered marble; Increase the temperature
(b)Answer: Concentration of a reactant in solution (or a catalyst, or pressure of gases).
concentration (of a reactant in solution) / adding a catalyst / pressure (of reacting gases)
(c)Answer: No: the same masses of marble and acid react, so the same volume of gas forms; the powder only makes the reaction faster.
no
the same mass of marble reacts (with the same acid) so the same volume of gas is produced; the powder only increases the rate
Question 2Medium4 marks
Two students investigated how the concentration of sodium thiosulfate solution affects the time for a black cross to disappear, viewed through the solution from above.
Student A repeated the experiment three times with 40 g/dm3 solution and got times of 21 s, 22 s and 21 s.
Student B, using a different batch of the same concentration of sodium thiosulfate solution and a different stopwatch, got a time of 23 s.
(a) What is meant by a result being repeatable?[1]
(b) What is meant by a result being reproducible?[1]
(c) Use the data to explain why student A's results are repeatable and the investigation is reproducible.[2]
Show the answer and mark scheme
(a)Answer: The same experimenter repeats the method with the same equipment and gets very similar results.
the same experimenter repeats the investigation using the same method and equipment and gets very similar results
(b)Answer: A different person, or different equipment, gets very similar results.
a different person, or different equipment, obtains very similar results
(c)Answer: Student A's three repeats (21, 22, 21 s) are all close together, showing repeatability; student B's result (23 s), with different equipment, is close to student A's results, showing reproducibility.
student A's repeated results are all close together (within 1 s of each other), showing repeatability
student B's result (23 s), obtained with different equipment, is close to student A's results, showing reproducibility
Question 3Hard6 marks
A factory manager wants to increase the rate of a reaction between two gases in an industrial reactor. The concentrations of the two gases cannot be changed.
Explain, using collision theory, how the manager could increase the rate of reaction. Suggest two different changes, and explain how each one increases the rate.[6]
Show the answer and mark scheme
Answer: See indicative content.
increase the temperature: particles move faster and collide more frequently
at a higher temperature, more particles have energy greater than or equal to the activation energy, so a greater proportion of collisions are successful
add a catalyst: this provides a different reaction pathway with a lower activation energy
so a greater proportion of collisions have enough energy to be successful, without needing to raise the temperature; the catalyst is not used up
if a solid catalyst is already used, increase its surface area (e.g. use pellets or a fine mesh rather than a lump), so more reacting particles collide with its surface per second
each change increases the frequency of successful collisions, increasing the rate
Marked with levels of response: the full level descriptors are in the app.