# Unit 5 Kinetics

## 5.11 Catalysis

Catalyst: chemical agent that speeds up a reaction without being consumed by the reaction → can be used over and over again           ○ Do not affect the free energy/enthalpy of a reaction!           ○ Reactions with a catalyst will typically require at least 2 steps...

## 5.10 Multistep Reaction Energy Profiles

The slowest (rate-determining) step in a mechanism will have the highest activation energy              ○ On graph, will have the highest peak Number of peaks = number of elementary steps Intermediates are found in minimums of graph; the transition states are found in...

Determining Rate Law When Slow Step is Not First Write rate law for slow step For fast step: set the rate of the forward reaction (k₁) = rate of reverse reaction (k₋₁) Then solve for the [intermediate] Plug in the equation into the slow step

## 5.8 Reaction Mechanism and Rate Law

The rate of a reaction can be no faster than the slowest step We cannot use the coefficients from a balanced, overall equation to deter mine the orders of a reaction          ○ Ex: We can use the coefficients from an elementary reaction determine the orders of a...

## 5.6 Reaction Profiles

Activation energy: Activated Complex - Change in Reactants (peak - line) Transition state/Activated complex: bonds are partially formed (shown on curve’s peak) Activation energy of reverse reaction: Forward Activation Energy - | ∆𝐻 | ∆H/∆E (total energy change/energy...

## 5.5 Collision Model

Collision Model: the energy (for breaking bonds of reactants) comes from the kinetic energies possessed by the reacting molecules before the collision            ○ Key idea: the rate of a reaction depends on the number of successful collisions and these collisions...

## 5.4 & 5.7 Elementary Reactions

Reaction Mechanisms A chemical equation does not tell us how reactants become products            ○ Simply a summary of the overall process Elementary steps: series of steps by which a chemical reaction occurs           ○ Cancel out identical species on opposite sides...

## 5.3 Concentration Changes Over Time

First-Order Rate Law Order = 1 → changing the reactant concentration has an identical effect on the reaction rate (same factor) Rate Law =  If a plot of ln[A] versus time is a straight line → reaction is first order Integrated First Order rate law: (on reference...