FunChem L17 Collision theory and rate equation

Chemical kinetics

Area of chemistry concerned with the speed or rate at which chemical rxn occurs

Chemical kinetics is the study of

Rate of chemical rxn

The factors that affect rates of rxns

The mechanisms by with rxns occur

Factors affecting rxn rates

Concentration

Temperature

Catalysis

Surface area

How does conc affect rate of rxn

Higher conc = faster rxn rate

How does temp affect rate of rxn

Higher temp = faster rxn rate

How does catalysis affect rate of rxn

usually speeds up rate of reaction

How does surface area affect rate of rxn

Larger surface area = faster rxn rate

What makes a collision effective

Molecular orientation

Energy of collisions

Frequency of collisions

Glancing blow

Less energetic no rxn

Head on collision

More energetic

Rxn takes place

What must the reacting molecules have

Correct orientation

Sufficient energy

Rate of reaction

Measures how fast a reactant is consumed or how fast a product is formed

How is rate of reaction expressed

change in concetration per unit time

Rate laws

Define the dependence of rate on concentrations

Differential rate law

Describes the realationship between reaction rate and reactant concentration

Integrated rate law

Describes the realationship between reactant concentration and time

Order of reaction

Describes the realationship between concentration of reactant and reaction time

0 order rxn

Rate is the same no matter what the concetration is

First order reaction

If you double the concetration you double the rate

Pseudo first order reaction

A reaction which is not first order but is made first order by increasing or decresing the concentration of one or the other reactant

Second order rxn

As the rate is dependent to reactant concentration raised to a power of 2