For the gas-phase isomerization of cyclopropane to propene

CHEMISTRY · Multi-part · A Level · Chemistry · Rate equations · Rate equations

Problem

For the gas-phase isomerization of cyclopropane to propene, the concentration of cyclopropane, C3H6(cyc)\mathrm{C_3H_6(cyc)}, obeys the empirical expression [C3H6(cyc)]=0.750e−0.0350t,[\mathrm{C_3H_6(cyc)}] = 0.750 e^{-0.0350 t}, where concentration is in mol L−1\mathrm{mol\,L^{-1}} and time tt is in seconds, for 0≤t≤120 s0 \le t \le 120\,\text{s}. Answer the following questions based on this relation. (1) Part 1: (a) Determine the instantaneous rate of disappearance of cyclopropane at t=40.0 st = 40.0\,\text{s}. (2) Part 2: (b) Calculate the average rate of disappearance of cyclopropane over the interval 30.0 s≤t≤50.0 s30.0\,\text{s} \le t \le 50.0\,\text{s}. (3) Part 3: (c) Explain why the two rates obtained in parts (a) and (b) are not identical, relating your explanation to the shape of the concentration-versus-time curve implied by the given expression.

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