kinetics

We use kinetics to work out mechanisms (the step by step process of a chemical reaction including bond making and breaking)

We also use it to find an equation that will tell us the rate for any set of qualities (rate law). We can use this to control how fast reactions take place which can be useful for industry (economically and safely)

Differential rate law (gradient)

Integrated rate law (curves for different orders in reactions with a single reactant). I.e. the equation for the time dependence of the concentraction of a single reactant.

In heterogeneous catalysts

Rate law only includes reactants in the rate determining step (when the reaction is multi step)

Can be used differentiate 2 related mechanisms for substituting one group for another. Sn1 & Sn2. (Eg if you substitute a then b onto x, the mechanism can be different than if you substituted b first)

Insitu:

Observation, spectroscopy, chemical sensor (eg pH meter, gas pressure)

Exsitu:

Quenching (stopping the reaction through cooling, dilution or neutralisation of a reaction). If you need to stop the whole reaction, the reaction needs to be done multiple times stopping at different moments

We can compare the experimental time dependence of the concentration to the predicted behaviour for different rate laws to find which one matches.

Half life is constant in first order reactions as the equation does not depend on concentration however it isn't constant for second order as the half-life depends on the concentration which changes throughout the reaction i.e. the half life cannot be constant

It is used to determine the order of a reaction without needing to run it for a long time, i.e. it's useful for slow reactions/ can’t use the integrated rate laws reliably over a short period

Used to find the rate law if there are multiple reactants present

If a reaction is first order according to the isolation method we can say that the reactant is pseudo first order i.e. the order of the overall reaction is one when all of the reactions are in in excess

Temperature has an exponential effect on the rate constant and this is shown through the Arrhenius equation

1. How frequently collisions occurr between molecules. (Collision theory gases)

2. Steric factor: Measure of the probability that molecules will collide with a collect correct geometry (Correct orientation). It takes a value between one and zero where one means any reaction can happen if enough energy is present.

Multiply these to get the pre-exponential factor this is approximately 10^7 to 10^15