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### Topic: Transition State Theory  (Read 4571 times)

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#### candidateof

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##### Transition State Theory
« on: April 27, 2012, 08:14:12 AM »
Hello,

I am having a hard time solving this question about the TST:

If the following gas-phase radical recombination reaction

.CH3+.CH3 C2H6

has a rate constant of 0.22 L mole-1 min-1 at 600oC. According to transition state theory, the reaction's rate at 900oC is:

a) 0.22 L mole-1 min-1
b) 0.37 L mole-1 min-1
c) 0.33 L mole-1 min-1
d) 0.30 L mole-1 min-1
e) 0.44 L mole-1 min-1

---------------------------------

I thought of using the equation:
k=(kBT/h)eG/RT
for the first T and get delta G at transition state, and then calculate the second k at 900 using the same G. But I think it is wrong since the G is changing with changing the temperature, right?

Regards,

#### Schrödinger

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##### Re: Transition State Theory
« Reply #1 on: April 27, 2012, 08:45:49 AM »
Hint 1 : Use the Arrhenius equation.
Hint 2 : What is the activation energy for reactions in which free radicals combine?
"Destiny is not a matter of chance; but a matter of choice. It is not a thing to be waited for; it is a thing to be achieved."
- William Jennings Bryan

#### candidateof

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##### Re: Transition State Theory
« Reply #2 on: April 27, 2012, 11:23:25 AM »
Hint 1 : Use the Arrhenius equation.
Hint 2 : What is the activation energy for reactions in which free radicals combine?

Dear Schrödinger,

Thank you for your helpful hints. Since the activation energy here is very small, we assume it is zero. Now, using the Arrhenius equation, the preexponential factor equal to k(Ea is zero). Taking the ratio of the two Arrhenius equations at different temperatures. we get:

ln(k1/k2)=E(-1/(RT1)+1/(RT2)) (since E=0)

(k1/k2)=1
k1=k2

But it is not correct, there must be somethin I am missing, right?

#### Schrödinger

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##### Re: Transition State Theory
« Reply #3 on: April 27, 2012, 03:31:26 PM »
The answer is not a) ? Well I'll be damned Which of the options is correct according to the book?
"Destiny is not a matter of chance; but a matter of choice. It is not a thing to be waited for; it is a thing to be achieved."
- William Jennings Bryan

#### candidateof

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##### Re: Transition State Theory
« Reply #4 on: April 27, 2012, 04:28:06 PM »
The answer is not a) ? Well I'll be damned Which of the options is correct according to the book?

LOL I don't have the right answer actually, but I have chosen this answer by chance in my quiz, and got zero  .

So this is your suggestion of solving this question, or I did not get you yet?

Thanks for sharing your information  ..

#### candidateof

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##### Re: Transition State Theory
« Reply #5 on: May 04, 2012, 05:29:21 AM »
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