I wanted to see how the rate of change of rate constant with temperature (dk/dT) changes with activation energy. I tried to do this with differentials: k=A*e(adsbygoogle = window.adsbygoogle || []).push({}); ^{-EA/RT}so

[tex]\frac{dk}{dT} = \frac{A E_A \cdot e^{-\frac{E_A}{RT}} } {RT^2}[/tex]

and then

[tex]\frac{d(\frac{dk}{dT})}{dE_A} = A \cdot e^{-\frac{E_A}{RT}} \cdot (\frac{1}{RT^2} - \frac{1}{R^2T^3})[/tex]

So long as E_{A}>RT, it appears that rate of change of rate constant with temperature would decrease for increasing activation energy (i.e. if you increase activation energy, then the rate constant is less susceptible to increasing when you change the temperature). E_{A}>RT would be almost universally the case I imagine - at 298 K that's less than 2.5 kJ/mol.

But this doesn't tally up with what we know, which is that for a given temperature increase, a greater activation energy leads to a greater increase in rate constant. e.g. if we write well-known

k_{2}/k_{1}= exp(-E_{A}/R * (1/T_{2}^{2}- 1/T_{1}^{2}))

and try some values we get this conclusion. So what went wrong or what is wrong with my idea to do it by differentiation?

**Physics Forums - The Fusion of Science and Community**

# Arrhenius equation

Know someone interested in this topic? Share a link to this question via email,
Google+,
Twitter, or
Facebook

- Similar discussions for: Arrhenius equation

Loading...

**Physics Forums - The Fusion of Science and Community**