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Kinetics

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Question 3

A pharmaceutical stability study measures the rate constant, kkk, for the decomposition of a vaccine's active protein at two different storage temperatures:

  • At a refrigeration temperature of T1=285 KT_1 = 285\text{ K}T1​=285 K, the rate constant is k1=3.12×10−6 s−1k_1 = 3.12 \times 10^{-6}\text{ s}^{-1}k1​=3.12×10−6 s−1.
  • At room temperature, T2=315 KT_2 = 315\text{ K}T2​=315 K, the rate constant is k2=1.18×10−4 s−1k_2 = 1.18 \times 10^{-4}\text{ s}^{-1}k2​=1.18×10−4 s−1.

The Arrhenius equation can be rearranged to calculate the activation energy, EaE_{\text{a}}Ea​:

ln⁡(k1k2)=EaR(1T2−1T1) \ln\left(\frac{k_1}{k_2}\right) = \frac{E_{\text{a}}}{R}\left(\frac{1}{T_2} - \frac{1}{T_1}\right) ln(k2​k1​​)=REa​​(T2​1​−T1​1​)

Calculate the value of the activation energy, EaE_{\text{a}}Ea​, in kJ mol−1\text{kJ mol}^{-1}kJ mol−1. Give your answer to 3 significant figures.

(The gas constant, R=8.31 J K−1 mol−1R = 8.31\text{ J K}^{-1}\text{ mol}^{-1}R=8.31 J K−1 mol−1)

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Markscheme

Kinetics Questions

  1. A Level
  2. /Chemistry
  3. /Kinetics

16 exam-style questions on AQA A Level Chemistry Kinetics, covering Collision theory, Maxwell–Boltzmann distribution, Effect of temperature on reaction rate, Effect of concentration and pressure, and Catalysts. Each one has a worked solution and a mark scheme showing where the marks go.

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