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Our final learning objective
of this kinetics unit, is to learn about catalysis.
We are going to explain what a catalysis is, what it does
and how it works down on a molecular level.
What is occurring, that allows
these catalysis to do what they need to do.
So what is a catalysis?
It is a substance that increases the rate
of a chemical reaction, without itself being consumed.
So it is going to speed up the reaction
and how ever much catalysis you put in at the beginning
that is how much you have at the end. How is that possible?
What happens is, that substance, that catalysis
reacts with an elementary step that is early in the mechanism. What happens is, that substance, that catalysis
reacts with an elementary step that is early in the mechanism.
So it is getting used, but later
in a subsequent step further down
in the mechanism it is getting regenerated.
So over all it is being used
and spit back out, and you do not see it being consumed.
Now that reason a catalysis works
is it is giving you a completely different mechanism
then what there was without the catalysis.
So it is becoming part of the elementary steps in out mechanism.
The rate determining step of that
has a lower activation energy.
So this is a simplification of what is
a catalysis is doing.
Picture A is the uncatalyzed form.
Picture B is the catalyzed form.
We see that it is lowering the activation energy.
Again, how does it do that? We see that it is lowering the activation energy.
Again, how does it do that?
It gives a complete different route
for the reactants to get into products
different elementary steps are occurring.
For the catalyzed form
the elementary step, that is the rate determining step
will have a lower activation energy barrier.
There are three general types of catalysts.
You have your heterogeneous and homogeneous catalyst
and then you have your enzymes.
Heterogeneous and Homogeneous, we will talk about them together
they are really defined by the state the catalyst is in.
Heterogeneous are in a different phase then their reactants.
This is what is sen in catalytic converters.
Often you have a solid catalysts and the gases pass through.
That is occurring in our catalytic converters. Often you have a solid catalysts and the gases pass through.
That is occurring in our catalytic converters.
The exhaust gases are coming
through that catalytic converter.
Catalytic converters are solid metals
that the gases passes through and it allows for
the combustion process to be oxidation
of those exhaust products to occur.
Homogeneous catalysts are int he same phase as your reactants.
For example they are all aqueous, or they are all in the gas phase.
So that would be a homogeneous catalyst. For example they are all aqueous, or they are all in the gas phase.
So that would be a homogeneous catalyst.
An enzyme, you will see if you take courses
in biochemistry for example, so they are enzymes
they help catalyze biochemical processes
that take place in your body.
They allow for these reactions to take place
with out having really high temperatures.
These are often very large and complex molecules
with molar masses in the thousands.
All the same aspects apply to
enzymes that apply to catalysts.
They give an alternate route for the reaction to take place.
They lower the activation energy.
They, themselves, do not get consumed in the overall process.
I just wanted you to see, when I say
they are large and complex
each one of those little knobs, that you are seeing there, are a different atom.
This is a very very large enzyme
in you body, and it give the name there of the activated enzyme.
This enzyme would be involved in a
biochemical process, within the body.
So this is the end of our kinetics unit.
Be sure to view any of the addition work problems
that I have prepared for you.
Practice those problems in the practice set.
Study these notes and make sure your
are really understand what is occurring
on the molecular view of things
and on the macroscopic scale.
Then when you done studying you will be ready to take the assessment
to show that they understand Then when you done studying you will be ready to take the assessment
to show that they understand
the kinetics unit.