A multistep mechanism converts reactant R to product P through two sequential…

CHEMISTRY · Multi-part · AP · Chemistry · Kinetics · Kinetics

Problem

A multistep mechanism converts reactant R to product P through two sequential elementary steps. Table 1 – Energetic data for the uncatalyzed pathway (energies are given relative to

R = 0\,\text{kJ mol}^{-1}

)

Step	$E_a$ ( $\text{kJ mol}^{-1}$ )	$\Delta H$ ( $\text{kJ mol}^{-1}$ )
1	75	$-20$
2	60	$-35$

Answer the following questions. In every written description of a graph, specify all axis labels, approximate numerical values for key points, and clearly indicate transition states and reaction intermediates. (a) Determine the overall enthalpy change,

\Delta H_{\text{overall}}

, for the conversion of R to P. Show your calculation. (b) Draw a fully labeled reaction energy profile for the mechanism on appropriately scaled axes. Indicate the energy of each transition state, the energy of the intermediate, and the overall energy change. (c) Identify the rate-determining step for the uncatalyzed mechanism. Justify your answer using numerical values from Table 1.

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