Free energy and industrial processes

We have often used the equation defining free energy changes, as  

As a rule, when calculating AG at temperatures other than 298 K, we have made the assumption that AH and AS are independent of temperature. That is, we have calculated free energy changes at any temperature T as  

1 The Gibbs-Helmholtz equation We start with equation 7.1, which asserts that  

Alternatively, for a reaction, we could modify this to read  

This expression has very great usefulness, and has already been exploited in the previous chapter. On introducing this into equation 6.3, we have one form of the Gibbs-Helmholtz equation  

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O Brien. 1235 Ohmic drop, 811, 1089, 1108 Ohmic resistance, 1175 Ohm s law, 1127. 1172 Open circuit cell, 1350 Open circuit decay method, 1412 Order of electrodic reaction, definition 1187. 1188 cathodic reaction, 1188 anodic reaction, 1188 Organic adsorption. 968. 978. 1339 additives, electrodeposition, 1339 aliphatic molecules, 978, 979 and the almost-null current test. 971 aromatic compounds, 979 charge transfer reaction, 969, 970 chemical potential, 975 as corrosion inhibitors, 968, 1192 electrode properties and, 979 electrolyte properties and, 979 forces involved in, 971, 972 977, 978 free energy, 971 functional groups in, 979 heterogeneity of the electrode, 983, 1195 hydrocarbon chains, 978, 979 hydrogen coadsorption and, 1340 hydrophilicity and, 982 importance, 968 and industrial processes, 968 irreversible. 969. 970 isotherms and, 982, 983... 

A catalyst has been found which gives adequate velocity at 500 C in the reaction CO 4- 2H2 = CH3OH. Estimate the order of magnitude of the pressure which would be required to make this reaction feasible as an industrial process. Tlie free energy and heats of formation are as follows (cal mol i... 

Exploring the relationship between Gibbs free energy and equilibrium further, consider again the Haber process for the production of ammonia (arguably one of the key industrial processes ever developed) ... 

Here we have demonstrated the essential features of a proposed model for determining tablet tensile strength from the properties of the component materials. The dependence of the Ryshkewitch-Duckworth parameters with tablet composition is consistent with the proposed model. Furthemore, the relation between particle surface free energy and tablet tensile strength is consistent with the available data. Calculations of the type discussed can be used to improve the efficiency of the formulation process. The model presented here is a step toward achieving quality by design in the pharmaceutical industry. 

The production of ammonia is of historical interest because it represents the first important application of thermodynamics to an industrial process. Considering the synthesis reaction of ammonia from its elements, the calculated reaction heat (AH) and free energy change (AG) at room temperature are approximately -46 and -16.5 KJ/mol, respectively. Although the calculated equilibrium constant = 3.6 X 108 at room temperature is substantially high, no reaction occurs under these conditions, and the rate is practically zero. The ammonia synthesis reaction could be represented as follows ... 

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