Lecture 8 Chemical Kinetics and Reaction Mechanisms

Flashcards covering reaction kinetics, rate laws, and reaction mechanisms based on lecture notes.

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Reaction Mechanism

A series of simple steps (i.e., elementary reactions) that reactants go through to become the final products of a reaction.

Elementary Reaction

A single reaction that cannot be broken down into simpler steps; particles interact directly through a collision or rearrangement/decomposition.

Validation of Reaction Mechanisms

Reaction mechanisms must be proposed and validated by experimental evidence; they can be discarded if they don't agree with observations.

Two Requirements for Plausible Mechanisms

When summed, the individual steps must add up to the overall balanced reaction, and the mechanism must account for the experimentally determined rate law.

Molecularity

The number of reactant particles that enter into an elementary reaction.

Unimolecular

Only one particle needed for reaction to proceed.

Bimolecular

Two particles need to collide for the reaction to proceed.

Termolecular

Three particles need to collide for the reaction to occur (RARE).

Rate Law of Elementary Reactions

The rate law of an elementary reaction can be determined directly from stoichiometry.

Reactive Intermediates (Intermediates)

Species formed in one elementary reaction and then consumed in a subsequent step; typically highly reactive.

Rate-Determining Step

The rate of the slowest step of the reaction mechanism determines the rate of the entire mechanism.

Slowest Step

It is the step with the highest activation energy (Ea).

Rate Law Agreement

The rate law of the rate-determining step must agree with the experimentally determined rate law of the overall reaction.

Rate Law of Elementary Reaction

Unlike an overall reaction, the rate law of an elementary reaction CAN be established directly from its stoichiometry.

Fast Equilibrium Step Solutions (continued)

Use the fact that step 1 is a fast equilibrium and substitute [N2O2] with measurable quantities