Catalyst changes...? #142 Destroyer

[pandalove89]

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Hey guys,

For question #142 on DAT destroyer in the chemistry section, it asks:

A catalyst will change?

a) Reaction Mechanism
b) Energy of activation
c) Specific rate constant
d) Two of these
e) All of the above


The answer is "e", but why?

I thought only temperature could affect the reaction mechanism and specific rate constant...

 

[rmm30]

Hey guys,

For question #142 on DAT destroyer in the chemistry section, it asks:

A catalyst will change?

a) Reaction Mechanism
b) Energy of activation
c) Specific rate constant
d) Two of these
e) All of the above


The answer is "e", but why?



No. You're mixing up equilibrium constant K with rate constant k. Temperature is the only thing that can change equilibrium constant K.
Rate constant k is the k you see in Rate Law.
Consider rxn: A + B -----> C; Rate law would be: Rate = k [A]^x ^y; where x and y are EXPERIMENTALLY derived and do not correspond to coefficients. By looking at that equation you can see that there are two ways to increase rate: 1) increase reactant concentration 2) increase k.
There are 2 ways to increase k: 1) raise temperature and 2) lower activation energy Ea with a catalyst. Mathmatically this is represented by the Ahhrenius Equation; k = Ae ^ (-Ea/RT). Ae is kind of like kmax. It's not really important that you understand the math behind it. The math just shows what was already stated: that increases in T and decreasing Ea will increase k.

 

[PooyaH]

Specific rate constant is NOT the same thing as Keq! Only temperature can change the Keq. But an enzyme or catalyst could def change reaction mechanism and specific rate constant.