catalysis vs intermediate

[Shreya Patel- 2D]

Hi guys,
I am watching Wednesday's lecture and am confused. What is the difference between catalysis and intermediate in a reaction?

[IsaacLaw1E]

Catalysts are there at the beginning and there at the end. Intermediates aren't there at the begin, are formed in-between, and aren't there at the end.
So for the ozone example, NO is with the oxygens, it is used up in-between the steps, and is then reformed. NO exists at the beginning and the end. It's a catalyst.
The single oxygen atom isn't there at the beginning. It is formed when NO2 reacts with O2. After it is formed, it is used to create O3 and no longer exists. It only existed in-between the steps. That makes it an intermediate.

[Sophia Spungin 2E]

And intermediate is something that is produced in one step of the reaction, and used in a subsequent step. It does not appear in the overall reaction as it is created and used in the process of the overall reaction.

A Catalyst is something that is necessary for the reaction to occur. It shows up on the reactants side of the reaction, is used, and then is reformed in a subsequent step of the reaction. Because it appears on both sides of the reaction, it also does not appear in the overall reaction.

In sum, I believe that an intermediate first a product and then a reactant whereas a catalyst is first a reactant and then a product.

Hope that helps!

[Darlene Lien 3E]

For a visual example:

A + B --> C + D
D + E --> B + F

B would be the catalyst
D would be the intermediate

[Becca Nelson 3F]

An intermediate is a species formed and then later consumed by the reaction.

A catalyst is not used by the reaction but is presented first on the reactants, then on the products side.

They will both cancel out of the overall equation.

The best way to determine is to see which side of the equation the catalyst/intermediate shows up on first. If it is first on the reactant side it is a catalyst. If it is first on the product side, it is an intermediate.

[abby hyman]

A catalyst is a species that is consumed and then produced
An intermediate is a species that is produced and then consumed
You would include the catalyst in the rate law but you would not include an intermediate

[Nishka Vipul 1J]

A catalyst is a substance that is first used up and then re-formed, whereas an intermediate is first formed then used up!

[Alexis Sanft 1E]

Catalyst will appear in reactants first and then later in products, so they are first consumed and then produced, so R-->P.
Intermediates will first appear in products, then reactants, so first produced then consumed, P-->R.

[keely_bales_1f]

Everyone above described a catalyst vs intermediate very well. I just thought I would give an example, so you can see their definitions in action...

A+B-->AB
AB+C-->AC+B

Based on these equations, we can see that AB is an intermediate, for it is first produced, then consumed. Species B is a catalyst for it is consumed first and then produced!

[Malakai Espinosa 3E]

Also a difference to note, catalysts can be included in your rate law if they are in the slow step, but intermediates cannot!

[AlyssaMaynard1C]

For a visual example:

A + B --> C + D
D + E --> B + F

B would be the catalyst
C would be the intermediate

is B the catalyst in both?

[Jeffrey Hablewitz 2I]

For a visual example:

A + B --> C + D
D + E --> B + F

B would be the catalyst
C would be the intermediate

is B the catalyst in both?

I think that this is showing the two elementary steps of the overall reaction A + E (+B) --> C + F (+B). In this case, B is a catalyst in the overall reaction because it appears in the overall reactants and the overall products. Hope this helps!

[LarisaAssadourian2K]

Hello! A catalyst is there from the very first set of reactants to the last set of products. An intermediate is something that is formed throughout the reaction, and it ends up getting consumed as well. It is not there at the beginning or the end.

[Sondia Luong 1C]

It's easier to remember if you think of catalysts and intermediates as opposites. An intermediate is produced in the reaction and is later consumed, while a catalyst is first consumed in a reaction and later produced.

[Pratika Nagpal]

For a visual example:

A + B --> C + D
D + E --> B + F

B would be the catalyst
C would be the intermediate

is B the catalyst in both?

I think that this is showing the two elementary steps of the overall reaction A + E (+B) --> C + F (+B). In this case, B is a catalyst in the overall reaction because it appears in the overall reactants and the overall products. Hope this helps!

why is D not the intermediate

[Pratika Nagpal]

Also a difference to note, catalysts can be included in your rate law if they are in the slow step, but intermediates cannot!

why is the rate law governed by the slow step

[Evelyn Silva 3J]

A catalyst always appears in the beginning and end of the reaction. An intermediate is formed and consumed during the reaction.

[Karina Grover 1A]

Functionally, catalysts lower the activation energy barrier of a reaction and thus, increase the rate constant and the reaction rate.

Catalysts are consumed and then produced in reactions so, overall, they are not consumed in reactions (they appear at the beginning and at the end).
Intermediates, on the other hand, are produced and then consumed in reactions.

[Ziyan Peng 3A]

catalysts are used and produced again so that you see it both at the beginning and at the end of reactions where as intermediates are produced and consumed.

[FrancescaHawkins2H]

An intermediate is something other than the reactants or products listed in the overall reaction, that is needed in order to get the desired products from the reactants. I think the hey point here is that an intermediate will not be present in the overall equation. Conversely, a catalyst will be listed on the reactants side of the chemical formula, although it is not a reactant. It is best identifiable because it doesn't go to forming products (instead it decreases the activation energy needed for the reactants to form the products).

[Eve Gross-Sable 1B]

An intermediate is produced and then consumed, while a catalyst is consumed and then produced.

[605823283]

A catalyst is consumed and then produced
An intermediate is produced and then consumed

[Vashe Sundar 3H]

A catalyst is substance that lowers the activation energy of a reaction, but it exists as a reactant at the beginning of the reaction and is produced later (i.e. it's regenerative). An intermediate is produced in the reaction and then is used as a reactant. The key difference is that an intermediate is produced, whereas a catalyst must be introduced.

[005754305]

Catalysts are added as a reactant and shows up as a product and they are not consumed but help speed up the rate of the reaction.
Intermediates are formed as a product and are used up int he reaction so don't show up in the reaction at the end as they are consumed.
Hope this helps!

[Arambula 1H]

A catalyst first appears as a reactant and is consumed and then produced again by the end of the reaction. An intermediate first appears as a product but is consumed by the end of the reaction. So while they both appear on both sides it of the reaction it just depends where they appear first.

[Carleigh Greenway 1D]

Also a difference to note, catalysts can be included in your rate law if they are in the slow step, but intermediates cannot!

why is the rate law governed by the slow step

The rate law is governed by the slow step because in any process, the step that is the slowest is going to determine the limit of how much the process can produce. For example, if you are making a bunch of pizzas with people at each station of making the pizzas such as dough kneading, putting the sauce on, and then the toppings, but one station is really slow, say the topping station, then you can only make as many pizzas in a certain amount of time that the topping station can do. The same thinking is used for the rate law in reactions. If there is a multiple step reaction, than the slow step will determine the overall rate, or rate law, of the reaction. Hope this makes sense!