Zero-Order Catalysts

[Isis_DW_3G]

In today's lecture when Dr. Lavelle mentions that catalysts are saturated in zero order reactions, what did this mean? This section kind of confused me overall.
Thanks!

[Edison Tham 3D]

Hi! If you think about it as enzymes and substrates, where catalysts are the enzymes and reactants are substrates, once all the catalysts are saturated, no more reactants can bind onto it (too many substrates, too little enzymes). So in zero order reactions, what he means by when catalysts are saturated, he is referring to how the reaction rate will not change no matter how much concentration of reactant is present.

[Melody Wu 2L]

Reactants bind to catalysts. So when a catalyst is saturated, it means they're all already bound to a reactant and thus no more reactant will bind to it (there is excess reactant and not enough catalyst). You can think of it as like a "buddy system" and all the catalysts have already found a reactant buddy but there's way more reactant than catalyst so a lot of reactant doesn't end up pairing up with a catalyst buddy. At this point, the reaction rate will not go any faster because it's reached its maximum.

[apurva-3E]

I think he basically means that the reactions that catalysts play a role in are zero order reactions, due to the fact that the reaction does not depend on the concentration of the reactant and how it varies. Therefore, for a zero order reaction, k is the driving factor in the reaction speed.

[Praneetha Kakarla 3A]

If it helps, you can think of it kind of like limiting reagents. If you have a catalyst and you add enough reactant to cover the entire catalyst, adding more reactant won't increase the rate of the reaction (the catalyst is like the limiting reagent & the reactant we're adding is in excess). The rate of the reaction is independent of the reactant concentration (just like how the amount of products formed in a reaction is dependent on the limiting reagent & not the reactant in excess).

[MariaCassol1L]

He means that when you have a reaction with catalysts the rate of reaction depends on the catalyst and not the reactant concentration as you have more reactants than catalysts, so the catalyst is always busy, and no matter how much you increase the reactant concentration by the rate of the reaction will not change as the number of catalysts will not change.

[Justin Nguyen 3E]

As everyone else said, when catalysts are saturated in zero-order reactions, they have bonded to the maximum amount of substrate possible to react, and as a result the rate of reaction is limited by the rate constant k.

[Stephanie Zhang 2K]

Hi! when catalysts are saturated, no matter how much more reactant/substrate are present in the solution, the rate will stay the same since the catalyst can't go any faster than it already is when it's saturated. That means that the reaction rate does not depend on the concentration of the reactant, which is why it is a zero-order reaction (this is the general definition for it, you can also see this since for a zero order reaction, when you plot [A] vs t you get a straight line; the reaction rate stays constant no matter the concentration). Hope this helped!

[Rob Tsai 2F]

A really simple way to think about is that if the catalyst/enzyme is saturated, it means it cannot cannot further speed up the reaction any further because all of its catalyzing power has been utilized. This means if a reaction that no matter how much reactant is present, the rate of the reaction will not depend on the concentration of the reactants, but rather k, the reaction rate constant. Hope this helps!

[David Jen 1J]

By saturation, he means that all the enzymes are currently in use and even by adding more of the reactant, the reaction rate wouldn't increase.