A multistep reaction has three transition states whose energies above the reactants are ,
CHEMISTRY · Single correct · A Level · Chemistry · Kinetics · Kinetics
Problem
A multistep reaction has three transition states whose energies above the reactants are 60kJ, 42kJ, and 58kJ, respectively. Which of the following best explains why the first elementary step exerts the greatest control over the overall reaction rate?
(a) Because the reaction products cannot form until the high-energy barrier of the final step (58kJ) is overcome, the overall rate is limited by the last elementary step.
(b) Because the first step is highly exothermic, the heat released during that step slows the molecules down, reducing the rates of the later steps.
(c) Because the first step has the largest activation energy, only a small fraction of reactant molecules can reach its transition state, so it is the slowest and controls the overall rate.
(d) Because the intermediates formed after the first step are too unstable to persist, they rapidly revert or convert to products, causing the subsequent steps to proceed more slowly.