Controlling reactions

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Question 1
Hard

The Maxwell-Boltzmann distribution curves for a gas-phase reaction at two different temperatures, T1 T_1\,T1​ and T2T_2T2​, are shown below, along with the activation energy values for the uncatalysed reaction (EaE_{\text{a}}Ea​) and the catalysed reaction (EcatE_{\text{cat}}Ecat​).

Maxwell-Boltzmann Distribution

Which of the following statements correctly explains how the reaction rate is controlled when the temperature is changed from T1 T_1\,T1​ to T2 T_2\,T2​ and a catalyst is added?

The temperature increase to T2T_2T2​ shifts the peak of the distribution to the right, increasing the most probable energy of the molecules, while the catalyst lowers the activation energy from EaE_{\text{a}}Ea​ to EcatE_{\text{cat}}Ecat​, greatly increasing the fraction of molecules with E≥EcatE \ge E_{\text{cat}}E≥Ecat​.

The catalyst lowers the activation energy from EaE_{\text{a}}Ea​ to EcatE_{\text{cat}}Ecat​ by shifting the distribution curve from T1T_1T1​ to T2T_2T2​, while increasing the temperature increases the number of successful collisions by increasing the total area under the curve.

The temperature increase to T2T_2T2​ lowers the activation energy from EaE_{\text{a}}Ea​ to EcatE_{\text{cat}}Ecat​, while the catalyst increases the average kinetic energy of the molecules, shifting the distribution curve to the right.

The transition from T1T_1T1​ to T2T_2T2​ increases the activation energy to EaE_{\text{a}}Ea​, while the catalyst increases the fraction of molecules exceeding this energy by shifting the peak of the Maxwell-Boltzmann distribution to a lower energy.

Controlling reactions Questions

  1. GCSE
  2. /Chemistry
  3. /Controlling reactions