Calculation of at Elevated Temperature

Method 2 If temperature is below about 150°C, the approximation that the heat capacity of reaction does not change, AjCp = ArCpxo can be used. In this case. Equation 4.21 can be combined with Equations 4.1 through 4.3 to derive the following expression  

Method 3 If temperature is above 150°C, the most accurate thermodynamic equation should be used  

Method 4 If temperature is slightly elevated above 25°C but still below about 75°C, the two last terms in Equation 4.30 can be canceled out because of a similar magnitude and opposite sign of the last two terms  

Note that the right-hand part of Equation 4.31 can be very confusing. It could mis-guidedly appear that A G° can be calculated at any elevated temperature using only AjHjo and A S. However, Equation 4.31 should never be used at temperatures above about 75°C. 

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