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Ea (activation energy) and constant k

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briggsinator2

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Question: so in Chad's videos it is suggested that an increase in Ea (activation energy) causes a decrease in the reaction coefficient k, because an increased Ea will decrease the rate. However, in Princeton Review it is suggested that thermodynamics (i.e. Ea) are independent of kinetics (i.e. k). However, it definitely is true that an increased Ea causes a decrease in k via the Arrhenius equation...how is it possible that thermodynamics are "independent" of kinetics if a thermodynamic factor like Ea can affect k? What did Princeton Review mean? Thanks!
 

gangazi

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I was wondering a similar thing... Chad mentions the only relationship between the Eq constant K and rate constant k as K=rate constant forward/rate constant reverse... And rate constant k is affected by Ea
 

Dmitry

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Princeton Review has probably made a mistake here. Ea is usually reduced in the presence of a catalyst or an enzyme, that will definitely speed up the forward and reverse reaction. The rate constant, k, will have to vary proportionally.
 

tommyngu

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Activation energy is actually a kinetic property.
Thermodynamics can be thought of like a state function. It looks at the reaction's state after it has occurred. You can find quantities like Gibb's free energy which is the energy released after a reaction has taken place which will tell you if a reaction would be considered spontaneous or not. But this doesn't tell you anything about how fast or easily the reaction occurs.
Kinetics looks at how a reaction occurs... Like how fast it occurs (rate) or how much energy was required to make it occur (activation energy).
So the two are independent.
 
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