IB Chemistry SL R2.2 How fast? The rate of chemical change questions

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Question 1

Paper 2Easy6 marks

A chemist compares the initial rate of a gas-phase reaction at two temperatures, with the same initial reactant concentrations. Figure 1 shows Maxwell–Boltzmann energy distributions for the reactant particles. The activation energy for the reaction is 8.0 kJ mol−18.0\ \mathrm{kJ\,mol^{-1}}

051015202530354000.020.040.060.080.10.120.140.160.180.20.22Energy, E / kJ mol-1Fraction of particles per kJ mol-1ABEa=8.0 kJ mol-1
(a)

State what is meant by the activation energy, EaE_a of a reaction.

[1]
(b)

Use Figure 1.

(i)

Identify which curve represents the higher temperature.

[1]
(ii)

Shade the area under this curve that represents particles with enough energy to react.

[1]
(iii)

Explain why the initial rate of reaction is greater at the higher temperature.

[2]
(c)

A catalyst is added to the reaction. On Figure 1, draw and label a vertical line to show the activation energy for the catalysed reaction.

[1]

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