TAILIEUCHUNG - Thermodynamics Interaction Studies Solids, Liquids and Gases 2011 Part 17

Tham khảo tài liệu 'thermodynamics interaction studies solids, liquids and gases 2011 part 17', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 790 Thermodynamics - Interaction Studies - Solids Liquids and Gases Thermodynamic basis for the construction of AGr x T diagrams To construct the AGO x T diagram f a particular reaction we must be able t compute its standard Gibbs energy in the whole temperature range spanned by the diagram. AGro -AH - TASro T AHr - AH298 J ACpdT K T ACo ASr AS298 J TdT K T dAHo 5 ACo dAH 2Cog 5 Cg _5Cg _Cs ACP - dT p Mc15 2 CP O2 5CP C12 cp m2o5 o 5g g s AH298 - 2H298 MC15 2 H298 O2 5H298 C12 H298 M2O5 o . 5 g - s AS298 - 2 S298 MC15 2S298 O2 5S298 C12 S298 M2O5 17 For accomp1ishing this task one needs a mathematica1 mode1 for the mo1ar standard heat capacity at constant pressure va1id for each participating substance for T varying between K and the fina1 desired temperature its mo1ar entha1py of formation H298 and its mo1ar entropy of formation S 98 at K For the most gas - so1id reactions both the mo1ar standard entha1py AHo and entropy of reaction AS do not depend strong1y on temperature as far no phase transformation among the reactants and or products are present in the considered temperature range. So the observed behavior is usua11y described by a 1ine Fig. 1 whose angu1ar coefficient gives us a measurement of AS and AHo is defined by the 1inear coefficient. Fig. 1. Hypothetica1 AGro x T diagram On the Chlorination Thermodynamics 791 Fig. 2. Endothermic and exothermic reactions Further for a reaction defined by Eq. 1 the number of moles of gaseous products is higher than the number of moles of gaseous reactants which based on the ideal gas model is indicative that the chlorination leads to a state of grater disorder or greater entropy. In this particular case then the straight line must have negative linear coefficient - AS 0 as depicted in the graph of Figure 1 . The same can not be said about the molar reaction enthalpy. In principle the chlorination reaction can lead to an evolution of heat exothermic process then AHo 0 or absorption of .

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