Lesson: Multi-Step Reaction Kinetics

In this lesson, we will learn how to use preequilibrium and steady-state approximations to calculate overall rate constants of multi-step reactions.

Worksheet: 8 Questions

Q1:

Write a balanced chemical equation for the overall reaction.

In the preequilibrium approximation, the rates of reactions 1 and 2 are equal. Use the preequilibrium approximation to find an expression for 𝑘 in terms of the elementary reaction rate constants.

In the steady-state approximation, the rates of change of [C] and [D] are zero. No assumptions are made regarding [B] or the rates of reactions 1 and 2. Use the steady-state approximation to find an expression for 𝑘 in terms of the elementary reaction rate constants.

Which condition must be satisfied for the preequilibrium and steady-state approximations to produce the same expression for 𝑘?

Q2:

The stoichiometry of the reaction depends on the relative rates of reactions 2 and 3. Based on the mechanism described, which of the following is not a balanced reaction equation?

Which condition must be satisfied for the steady-state approximation to be valid?

Use the steady-state approximation to find an expression for the rate of formation of C in terms of [A] and the elementary reaction rate constants.

Use the steady-state approximation to find an expression for the rate of formation of E in terms of [A] and the elementary reaction rate constants.

Q3:

Write a balanced chemical equation for the overall reaction.

The reaction is found to be of the second order with respect to A and the first order with respect to C. Identify the rate-determining step for the reaction.

Use the preequilibrium approximation to find an expression for 𝑘 in terms of [A] and [C] and the elementary reaction rate constants.

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