Steady rxn vs. fast to slow rxn?

[Sammy1024]

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Are there some reactions that remain steady over time and then stop once they're at equilibrium?

I did some questions where a compound was added to a solution and so the rxn happened quickly but got slower over time until it stopped. However, i've sometimes come across situations where it's a steady graph until it abruptly stops but can't remember what it referred to.

 

[The Brown Knight]

Wild guess here, but are you maybe referring to Michaelis-Menten kinetics? They are linear at low substrate concentrations but taper off at higher ones.

 

[AmishExpressWay]

Zero order reactions are constant over time, since zero order kinetics don't care about no molecule concentration.
rate = k for zero order as opposed to
rate = k[A] for first order
First order reaction rates decrease as they go on because rate is related to the concentration of A in solution, which is used up as the reaction progresses.
Zero order kinetics, on the other hand, is a pretty cool guy because eh has a constant reaction rate and doesn’t afraid of anything.

 

[Sammy1024]

So would you say that linear graphs are usually in physics depending on the equation being used? I feel that in most gchem stuff, it is not linear, except for I guess kinetic like equations. Also, second order would not be linear right?

 

[NextStepTutor_1]

So would you say that linear graphs are usually in physics depending on the equation being used? I feel that in most gchem stuff, it is not linear, except for I guess kinetic like equations. Also, second order would not be linear right?

For physics and gen chem (basically for everything really) the graph shape depends on the context (naturally). But for the sake of trying to distinguish graphs within the context of MCAT info, you can think of using an equation to explain physics graphs (though a lot of the time it's quicker and easier to use intuition). It's very difficult to make generalities and I'm not comfortable telling you that most gen chem graphs won't be linear, but it's important to note that linear graphs are normally a reflection of ideal situations.
And yes, second order graphs (whether you're looking at the graph for the rate of the reaction or the half life) will not be linear.

Cheers!



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