16.2 Activation Energy

Three experiments were carried out at a temperature, T₁,  to investigate the rate of the reaction between compounds F and G. The results are shown in the table below:

	Experiment 1	Experiment 2	Experiment 3
Initial concentration of F / mol dm-3	1.71 x 10-2	5.34 x 10-2	7.62 x 10-2
Initial concentration of G / mol dm-3	3.95 x 10-2	6.24 x 10-2	3.95 x 10-2
Initial rate / mol dm-3 s-1	3.76 x 10-3	1.85 x 10-2	1.68 x 10-2

Use the data in the table to deduce the rate equation for the reaction between compounds F and G.

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Use the information in the table in part (a) to calculate a value for the rate constant, k, for this reaction between 0.0534 mol dm^-3 F and 0.0624 mol dm^-3 G. 

Give your answer to the appropriate number of significant figures.

State the units for k.

(If you did not get an answer for (a), you may assume that rate = k [F]² [G]². This is not the correct answer)

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The Arrhenius equation shows how the rate constant, k, for a reaction varies with temperature, T.

For the reaction between 0.0534 mol dm^-3 F and 0.0624 mol dm^-3 G at 25 °C, the activation energy, E_a, is 16.7 kJ mol^–1. 

Use section 2 of the data booklet and your answer to part (b) to calculate a value for the Arrhenius constant, A, for this reaction. 

Give your answer to the appropriate number of significant figures.

(If you did not get an answer for (b), you may assume that k has a value of 4.97. This is not the correct answer)

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The temperature of the reaction is increased to twice the original temperature, T₁.
The value of k increases to 0.28 mol^-1 dm³ s^-1 at this new temperature.
 

The rate constant for a reaction doubles when the temperature is increased from 25.0 °C to 35 °C.

Calculate the activation energy, E_a, in kJ mol⁻¹ for the reaction using section 1 and 2 of the data booklet.

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The rate constant is 6.2 x 10³ s^-1 when the temperature is reduced by a factor of a fifth from the original starting temperature, 25 °C.

Calculate the rate constant, in min^-1, using sections 1 and 2 of the data booklet.

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A different reaction route is used which reduces the activation energy of the reaction. 

Explain how the rate constant calculated in part(b) would differ.

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