Chad's video question: Changing the "rate" without chaning the rate constant"k"?

[famousbanker]

In Chad's video on "kinetics: mechanisms and rate constants" he says you can increase the rate without increasing the rate constant by changing the concentration of the reactants. In all other scenarios, anything that changes the rate also changes the rate constant.

Is he saying that if you change the concentration of reactants (or products), you will change the equilibrium constant "K" but you will not change the rate constant "k"?

I just want to make sure I fully understood what he was saying. Thank you in advance for your help.

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[SN1]

In Chad's video on "kinetics: mechanisms and rate constants" he says you can increase the rate without increasing the rate constant by changing the concentration of the reactants. In all other scenarios, anything that changes the rate also changes the rate constant.

Is he saying that if you change the concentration of reactants (or products), you will change the equilibrium constant "K" but you will not change the rate constant "k"?

I just want to make sure I fully understood what he was saying. Thank you in advance for your help.

Rate = K [reactant 1] [reactant 2], ...

so yeah looking at the formula you can increase rate by changing the concentration of the reactant.

the arhenius equation:
K= Ae^Ea/rt

only activation energy and temperature can affect rate constant "k" but a catalyst which lowers activation energy will also affect k and as a result affect the Rate.

 

[SpecterGT260]

K is just a constant which dictates the magnitude of effect that the concentrations has on the rate. K is not the rate. And all constants are always constant.... they NEVER change. Sorry if this seems overly simplistic.... just look at the equation above and you should see how concentration will impact rate without ever affecting k

 

[SN1]

K is just a constant which dictates the magnitude of effect that the concentrations has on the rate. K is not the rate. And all constants are always constant.... they NEVER change. Sorry if this seems overly simplistic.... just look at the equation above and you should see how concentration will impact rate without ever affecting k

K can be changed if there is a temperature change no?

 

[SpecterGT260]

K can be changed if there is a temperature change no?

The k values are usually tabulated at standard conditions.... so technically yes. But this constitutes an exception. The important thing to understand here is that constants are always used as correction factors within systems where parts and responses are associated.


If we want to get really nit picky you will have to take pchem or some other physics and calculus based application course. You will find that many constants contain variable terms but are standardized for use. i.e. derivation of many such constants requires inputs of things like temp. At specific steps along the process the dude holding the chalk gets fed up with all the letters, circles about 10 of them, and attaches his name to the specific number they generate.

 

[SN1]

The k values are usually tabulated at standard conditions.... so technically yes. But this constitutes an exception. The important thing to understand here is that constants are always used as correction factors within systems where parts and responses are associated.


If we want to get really nit picky you will have to take pchem or some other physics and calculus based application course. You will find that many constants contain variable terms but are standardized for use. i.e. derivation of many such constants requires inputs of things like temp. At specific steps along the process the dude holding the chalk gets fed up with all the letters, circles about 10 of them, and attaches his name to the specific number they generate.

Yeah I don't think the DAT is gonna go very deep with this

do you mind answering my question about redox? You seem very knowledgable

http://forums.studentdoctor.net/showthread.php?t=919376

 

[SpecterGT260]

Ya. The MCAT didn't either 👍 it was more of an "fyi" 😀

 

[yappy]

This:

Rate = K [reactant 1] [reactant 2], ...

so yeah looking at the formula you can increase rate by changing the concentration of the reactant.

the arhenius equation:
K= Ae^Ea/rt

only activation energy and temperature can affect rate constant "k" but a catalyst which lowers activation energy will also affect k and as a result affect the Rate.

Kinetics:

K can be changed via the Arhenius equation via

-Temp
-changing the Activation energy via a catalyst



Also, If you change the concentration of the reactants you can change the rate of the reaction but K will remain the same value per: Rate = K [R1][R2]

Be careful not to misunderstand this K, rate constant, from the "equilibrium constant" K eq which is equal to the concentration of the products over the reactants raised to their stoich coefficiant. They're two different fields of study: Kinetics is different than chemical equilibrium.

 

[SN1]

This:


Kinetics:

K can be changed via the Arhenius equation via

-Temp
-changing the Activation energy via a catalyst



Also, If you change the concentration of the reactants you can change the rate of the reaction but K will remain the same value per: Rate = K [R1][R2]

Be careful not to misunderstand this K, rate constant, from the "equilibrium constant" K eq which is equal to the concentration of the products over the reactants raised to their stoich coefficiant. They're two different fields of study: Kinetics is different than chemical equilibrium.

Was my explanation right?

 

[SpecterGT260]

Yeah I don't think the DAT is gonna go very deep with this

do you mind answering my question about redox? You seem very knowledgable

http://forums.studentdoctor.net/showthread.php?t=919376

I was a chem major. I saw that thread but its irritating to read without sub and superscripts 😉 ill look at it again in the morning

 

[SN1]

I was a chem major. I saw that thread but its irritating to read without sub and superscripts 😉 ill look at it again in the morning

Lol. Thanks

 

[yappy]

I thought so. I just wanted to add in the part about Keq vs K rate constant as students mix those up a lot.

Was my explanation right?

 

[famousbanker]

Thank you very much for your responses. I have not logged on in a while, so Im sorry for the slow reply