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Rate law test with answers for AP Chemistry (free PDF download)

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Quick answer: A rate law, rate = k[A]^m[B]^n, shows how reaction rate depends on reactant concentrations, with orders found by experiment. This AP Chemistry test on rate law has 8 questions worth 20 marks, to do in 45 minutes: rate law from data, units and first-order calculation. The mark scheme is on a separate page; free printable PDF.

Rate law test with answers for AP Chemistry (free PDF download)

This test lasts 45 minutes and covers rate laws, orders, integrated rate laws and half-lives. Calculators are allowed. Show your working and give units; marks are shown for each question and the total is 20.

Level: AP Chemistry · Curriculum: AP Chem Unit 5

Time: 45 minutes · 8 questions · Total: 20 marks · Calculator allowed

Question 1 Rate law from data (3 marks)

For ICl + H₂ → products, initial rates: (1) [ICl] = 0.10 M, [H₂] = 0.10 M, rate = 1.5 × 10⁻³ M/s; (2) [ICl] = 0.20 M, [H₂] = 0.10 M, rate = 3.0 × 10⁻³ M/s; (3) [ICl] = 0.20 M, [H₂] = 0.40 M, rate = 1.2 × 10⁻² M/s.
  1. Determine the order in each reactant. (2 marks)
  2. Calculate k. (1 mark)

Question 2 Units (2 marks)

  1. Give the overall order of the reaction in Question 1 and the units of k. (1 mark)
  2. State the units of k for a first-order reaction. (1 mark)

Question 3 First-order calculation (3 marks)

A first-order reaction has k = 5.0 × 10⁻⁴ s⁻¹ and [A]₀ = 0.250 M.
  1. Calculate [A] after 1200 s. (2 marks)
  2. Calculate the half-life. (1 mark)

Question 4 Graph reading (2 marks)

Curve of concentration against time passing through 1.20 M at 0 s, 0.60 M at 30 s and 0.30 M at 60 s03060900.00.40.81.2time (s)[A] (M)
Concentration of A with time.
  1. Use the graph to find the half-life and state the order. (1 mark)
  2. Calculate k. (1 mark)

Question 5 Second-order time (3 marks)

A second-order reaction has k = 0.40 M⁻¹ s⁻¹ and [A]₀ = 0.30 M. Calculate the time for [A] to fall to 0.10 M.

Question 6 Explaining the effect of concentration (2 marks)

Explain, using collisions, why raising the concentration of a reactant usually increases the rate.

Question 7 Plots (2 marks)

A student plots [A], ln[A] and 1/[A] against time. Only the ln[A] plot is a straight line.
  1. State the order. (1 mark)
  2. State what the slope of the line represents, including its sign. (1 mark)

Question 8 Order from half-lives (3 marks)

A reaction has half-lives of 40 s at [A]₀ = 0.80 M, 80 s at 0.40 M and 160 s at 0.20 M.
  1. Determine the order and justify it. (1 mark)
  2. Calculate k with units. (2 marks)

See the rate law test answers and mark scheme

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