Rate of reaction: past paper questions
Real questions on rate of reaction
The newest 20 of 441 written questions. Open one to see it on the real paper.
- 9701/41 · May/June 2026 · Q3a[1]
Complete Table 3.1. Table 3.1 order with respect to [NO] order with respect to [H 2 ] overall order
See it on the paper → - 9701/41 · May/June 2026 · Q3b[2]
In experiment 1, the rate of the reaction is 2.80 × 10 –10 mol dm –3 s –1 when [NO] is 5.00 × 10 –2 mol dm –3 and [H 2 ] is 8.00 × 10 –2 mol dm –3 . Calculate the value of the rate constant, k, in experiment 1. State the units of k. k = units =
See it on the paper → - 9701/41 · May/June 2026 · Q3c(i)[1]
A graph of [H 2 ] against time for experiment 2 shows that the reaction has a constant half-life. Explain why the graph shows a constant half-life, referring to: • • the overall order of the reaction under these conditions the reason why this is the overall order under these conditions.
See it on the paper → - 9701/41 · May/June 2026 · Q3c(ii)[2]
Calculate the half-life, in s, of the reaction in experiment 2 and state the time taken, in s, for the value of [H 2 ] to fall to 7.50 × 10 –5 mol dm –3 . half-life = s time taken for [H ] to fall to 7.50 × 10 –5 mol dm –3 = s
See it on the paper → - 9701/41 · May/June 2026 · Q3d(i)[2]
Complete the mechanism by writing an equation for step 2.
See it on the paper → - 9701/41 · May/June 2026 · Q3d(ii)[1]
It can be deduced that step 1 is not the rate-determining step of the reaction. Explain why.
See it on the paper → - 9701/22 · October/November 2025 · Q3c[1]
Alkanes with low relative molecular mass, M r , are more useful than those found in heavier crude oil fractions. Name the process that is used to obtain alkanes with low M r from heavier crude oil fractions.
See it on the paper → - 9701/41 · October/November 2025 · Q3b(i)[4]
Use the information in Table 3.1 to deduce the rate equation for this reaction. Explain your reasoning.
See it on the paper → - 9701/41 · October/November 2025 · Q3b(ii)[2]
Use your rate equation from (b)(i) and the data from Experiment 1 to calculate the rate constant, k, for this reaction. Include the units of k. k = units
See it on the paper → - 9701/41 · October/November 2025 · Q3c(i)[2]
Use Fig. 3.1 to calculate two half-lives, t 1 , to show that the reaction is first order.
See it on the paper → - 9701/41 · October/November 2025 · Q3c(ii)[1]
Use your answer to (c)(i) to calculate the rate constant, k, for the decomposition of azomethane. k = s –1
See it on the paper → - 9701/42 · October/November 2025 · Q2b[2]
rate = k [CH 3 CHO][NO 2 ] Under certain conditions, when the concentrations of both CH 3 CHO and NO 2 are 0.200 mol dm –3 , the rate of the reaction is 1.53 × 10 –4 mol dm –3 s –1 . Calculate the value of the rate constant, k, under these conditions. Give the units of k. k = units (b) The rate equation for the reactio...
See it on the paper → - 9701/42 · October/November 2025 · Q2c[1]
The reaction mixture described in (b) is monitored over a period of time. Predict whether the graph of [NO 2 ] against time shows a constant half-life. Explain your answer. prediction explanation
See it on the paper → - 9701/43 · October/November 2025 · Q3a[1]
Solid manganese( IV ) oxide, MnO 2 , catalyses the decomposition of hydrogen peroxide. 2H 2 O 2 (aq) 2H 2 O(l) + O 2 (g) State the type of catalysis for this reaction. Explain your answer.
See it on the paper → - 9701/43 · October/November 2025 · Q3b(i)[4]
Use the information in Table 3.1 to deduce the rate equation for this reaction. Explain your reasoning.
See it on the paper → - 9701/43 · October/November 2025 · Q3b(ii)[2]
Use your rate equation from (b)(i) and the data from Experiment 1 to calculate the rate constant, k, for this reaction. Include the units of k. k = units
See it on the paper → - 9701/43 · October/November 2025 · Q3c(i)[2]
Use Fig. 3.1 to calculate two half-lives, t 1 , to show that the reaction is first order.
See it on the paper → - 9701/43 · October/November 2025 · Q3c(ii)[1]
Use your answer to (c)(i) to calculate the rate constant, k, for the decomposition of azomethane. k = s –1
See it on the paper → - 9701/53 · October/November 2025 · Q2a[1]
Suggest why the student adds 50 cm 3 of the gas being tested to the syringe in step 2 and then removes this gas in step 3.
See it on the paper → - 9701/53 · October/November 2025 · Q2b(ii)[1]
Identify the dependent variable in this experiment.
See it on the paper →
What examiners said
Many candidates did not understand that a large concentration of CH 3COCH3 was used to keep its concentration constant so that it did not affect the rate. A common error was ‘to allow the reaction to go to completion’.
— Examiner report, February/March 2025, 9701/42 Q2(a)(i) (Cambridge)
Some very good answers were seen. On questions of this type candidates must ensure: • they identify the order with respect to the reactant that must be addressed first - in this case it was [H+] • they clearly identify which experiments each part of their explanation refers to • answers rely on explanation, not on annotations on the table.
— Examiner report, February/March 2025, 9701/42 Q2(a)(ii) (Cambridge)
Some answers referred to constant half-life without presenting supporting evidence. It should be noted that ‘170 s and 330 s’ is not supporting evidence. ‘The time taken to halve from 100% to 50% is 170 s, the time taken to halve from 50% to 25% is 160 s’ is supporting evidence.
— Examiner report, February/March 2025, 9701/42 Q2(a)(iii) (Cambridge)
Past papers, syllabus and examiner reports © UCLES (Cambridge University Press & Assessment). Questions are matched to topics from the official syllabus. AssessPro is independent and not endorsed by Cambridge.