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Topic: Decomposition reaction kinetics  (Read 3436 times)

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Offline shmdan

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Decomposition reaction kinetics
« on: January 04, 2010, 11:45:22 AM »
hello, can anyone help me in this, please:

i'm giving general rate equation as follows:

dw/dt=A(1-w)n exp(-Ea/RT)

where w is the fractional weight loss of a polymer sample at time t (0<=w<=1 ),   is the decomposition rate (or weight loss) rate (min-1), T is the absolute temperature at time t (K), Ea is the activation energy (J/mol), R is the gas constant (8.314 J/mol.K), A is the frequency factor and n is the decomposition reaction order.

i have some sample data for T and with the corresponding w, dw/dt values.
Where the required are to find n, Ea, and A.
My question is that are these values (Ea, n and A ) are constants over the problem or they are change dynamically in same sort of equation that related to T?!


Thanks in advance.

Offline shmdan

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Re: Decomposition reaction kinetics
« Reply #1 on: January 07, 2010, 03:39:06 PM »
  ::)

Offline OrganicSynthesis

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Re: Decomposition reaction kinetics
« Reply #2 on: January 10, 2010, 02:17:50 PM »
Well, regardless of what the temperature is for a reaction, the activation energy will always stay the same so I don't see how Ea is a function of temperature. However, n is a function of temperature in that different temperatures will change the rates at which substances decompose. However, if temperature is constant, I don't see why n would change. In terms of A, well A is the amount of substance you are originally starting with so despite the temperature, you should always start with the same amount of substance.

Offline yempski

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Re: Decomposition reaction kinetics
« Reply #3 on: April 30, 2010, 12:52:34 AM »
n, Ea and A are constants.

The constants could be solved by graphing ln(dw/dt) versus 1/T or by using the SOLVER addin in excel.

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