Topic 16 Kinetics HL
16.1 Rate expressions

This video provides an introduction to rate expressions.

16.1 Orders of reaction

Understandings:
The order of a reaction can be either integer or fractional in nature. The order of a reaction can describe, with respect to a reactant, the number of particles taking part in the ratedetermining step. Applications and skills: Deduction of the rate expression for an equation from experimental data and solving problems involving the rate expression. Note that the IB sometimes refers to orders of reaction as partial orders of reaction. In this video, I use the term orders of reaction. 
16.1 Reaction mechanisms

This video covers how to deduce to the overall equation from the reaction mechanism and also how to deduce the rate expression from the elementary steps.

16.1 Ratedetermining step

Understandings:
Reactions may occur by more than one step and the slowest step determines the rate of reaction (rate determining step/RDS). 
16.1 Energy level profiles

This video shows how to identify the transition states and intermediates in an energy level profile.

16.1 Molecularity

Understandings:
The molecularity of an elementary step is the number of reactant particles taking part in that step. 
16.1 Sketch, identify and analyse graphical representations for zero, first and secondorder reactions.

Applications and skills:
Sketching, identifying, and analysing graphical representations for zero, first and second order reactions. 
16.1 Catalysts

Understandings:
Catalysts alter a reaction mechanism, introducing a step with lower activation energy. Guidance: Catalysts are involved in the ratedetermining step. 
16.2 The Arrhenius equation
Note that in the video, I use the term 'fraction of collisions with energy equal to or greater than the activation energy'. This is the same as saying 'the fraction of particles with energy equal to or greater than the activation energy'. So as temperature increases the fraction of particles with energy equal to or greater than the activation energy also increases (the IB prefers to use this expression).
Note that the IB definition of the Arrhenius constant (A) indicates the frequency of collisions and the probability that collisions have proper orientations.

Understandings:
The Arrhenius equation uses the temperature dependence of the rate constant to determine the activation energy. The frequency factor (or preexponential factor) (A) takes into account the frequency of collisions with proper orientations. 
16.2 Effect of temperature in the rate constant k

Applications and skills:
Describing the relationships between temperature and rate constant; frequency factor and complexity of molecules colliding. 
16.2 Calculating activation energy

Understandings:
A graph of 1/T against ln k is a linear plot with gradient – Ea / R and intercept, lnA. Applications and skills: Analysing graphical representation of the Arrhenius equation in its linear form 