A liquid-phase reaction can follow one of three mutually exclusive pathways that all…

CHEMISTRY · Multi-part · A Level · Chemistry · Kinetics · Kinetics

Problem

A liquid-phase reaction can follow one of three mutually exclusive pathways that all yield the same products. • Pathway X (uncatalyzed): Ea=85 kJ mol−1,  A=4.0×1011 s−1E_a = 85\,\text{kJ\,mol}^{-1},\;A = 4.0\times10^{11}\,\text{s}^{-1} • Pathway Y (homogeneous catalyst C): Ea=60 kJ mol−1,  A=4.0×1011 s−1E_a = 60\,\text{kJ\,mol}^{-1},\;A = 4.0\times10^{11}\,\text{s}^{-1} • Pathway Z (heterogeneous catalyst on a solid surface): Ea=45 kJ mol−1,  A=2.0×1011 s−1E_a = 45\,\text{kJ\,mol}^{-1},\;A = 2.0\times10^{11}\,\text{s}^{-1} (a) At 310 K determine which pathway produces the largest rate constant. Support your answer with an appropriate calculation. (b) Derive an expression for the temperature TeqT_{\text{eq}} at which kY=kZk_Y = k_Z, and calculate the numerical value of TeqT_{\text{eq}}. (c) Discuss how the difference in pre-exponential factors influences catalyst selection when the reaction is carried out near TeqT_{\text{eq}}. Include molecular-level reasoning in your discussion.

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