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Rate equations

From Mock A · Paper 1: Inorganic and Physical Chemistry
5.15 marks
The initial rate of the reaction between A and B was measured.
Experiment[A] / mol dm⁻³[B] / mol dm⁻³Rate / mol dm⁻³ s⁻¹
10.100.102.0 × 10⁻⁴
20.200.108.0 × 10⁻⁴
30.100.204.0 × 10⁻⁴
Deduce the rate equation and calculate the rate constant, with units.
From Mock A · Paper 1: Inorganic and Physical Chemistry
5.24 marks
The rate constant is 0.20 at 300 K and 0.80 at 320 K. Use ln k = ln A - Ea/RT to calculate the activation energy in kJ mol⁻¹.
From Mock A · Paper 1: Inorganic and Physical Chemistry
5.33 marks
Explain why the rate equation suggests the rate-determining step involves two particles of A and one of B, and suggest why a single-step mechanism is unlikely.
From Mock A · Paper 3: Practical skills, all content and multiple choice
2.14 marks
In an iodine clock experiment, the time for the blue-black colour to appear is measured at different concentrations of potassium iodide. Explain why 1/time can be used as a measure of initial rate and why only a small amount of sodium thiosulfate is added.
From Mock A · Paper 3: Practical skills, all content and multiple choice
2.23 marks
A graph of 1/t against [KI] is a straight line through the origin. State the order with respect to iodide and explain.
From Mock A · Paper 3: Practical skills, all content and multiple choice
141 mark
The rate equation is rate = k[X]². What happens to the rate when [X] is tripled?
From Mock B · Paper 1: Inorganic and Physical Chemistry
9.13 marks
Initial rates for A + B → products (data are illustrative, written for this paper):
Exp[A] / mol dm⁻³[B] / mol dm⁻³Rate / mol dm⁻³ s⁻¹
10.100.102.0 × 10⁻⁴
20.200.108.0 × 10⁻⁴
30.100.204.0 × 10⁻⁴
Deduce the order with respect to A and B and write the rate equation.
From Mock B · Paper 1: Inorganic and Physical Chemistry
9.23 marks
Calculate the rate constant, k, with units.
From Mock B · Paper 1: Inorganic and Physical Chemistry
9.32 marks
A plot of ln k against 1/T has a gradient of −6000 K. Calculate the activation energy in kJ mol⁻¹.
From Mock B · Paper 3: Practical skills, all content and multiple choice
2.13 marks
In an iodine clock reaction, explain how the time for the blue-black colour to appear is used to measure the initial rate.
From Mock B · Paper 3: Practical skills, all content and multiple choice
2.24 marks
Results (data are illustrative, written for this paper):
[H₂O₂] / mol dm⁻³0.0200.0400.0600.080
Time / s120604130
Calculate 1/t for each and deduce the order with respect to H₂O₂.
From Mock B · Paper 3: Practical skills, all content and multiple choice
191 mark
The units of a first-order rate constant are
From Mock C · Paper 1: Inorganic and Physical Chemistry
9.13 marks
The rate equation for 2NO + O₂ → 2NO₂ is rate = k[NO]²[O₂]. Explain the effect on the rate of doubling [NO] and halving [O₂].
From Mock C · Paper 1: Inorganic and Physical Chemistry
9.23 marks
Explain how the rate-determining step relates to the rate equation, using a reaction whose rate equation is rate = k[(CH₃)₃CBr].
From Mock C · Paper 2: Organic and Physical Chemistry
15.14 marks
The decomposition of N₂O₅ is first order. Its concentration fell from 0.0800 to 0.0400 mol dm⁻³ in 690 s (data are illustrative, written for this paper). Calculate the half-life and the rate constant.
From Mock C · Paper 3: Practical skills, all content and multiple choice
5.13 marks
A student measures the rate of reaction of magnesium with acid by collecting gas in a syringe. Explain how the initial rate can be found from a volume–time graph.
From Mock C · Paper 3: Practical skills, all content and multiple choice
181 mark
A zero-order reactant's concentration–time graph is
Score 0 / 50 · 0 of 17 marked

This paper is written by Plasmo in the style of the AQA A-Level Chemistry exam. It is not a past paper and is not produced or endorsed by the exam board.

Rate equations Exam Questions: AQA A-Level Chemistry | Plasmo