Chemical Forums
Chemistry Forums for Students => Physical Chemistry Forum => Topic started by: shmdan on January 04, 2010, 11:45:22 AM
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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.
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::)
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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.
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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.