Chemical change, direction significance

The use of AG as a criterion for deciding the direction of a chemical change has been briefly mentioned. AG"" refers to the reaction with both products and reactants in their standard states and industrial processes are, of course, often carried out under conditions far removed from standard. The significance of AG"" in relation to the technical feasibility of a reaction is illustrated in Table 1 where it is seen that AG = + 20 kJ mol" means an equilibrium constant of 3 x 10 at 298 K. With such a small equilibrium constant, a reaction is unlikely to be of much industrial value. At 2000 K, however, the same value of AG"" leads to an equilibrium constant of 0.3, potentially a very much more attractive situation. 

Since the coordinates log/Cf and log/<,- are independent of each other, a correlation between log/cf and log/ ,- as in Equation (29) would demonstrate the existence of a linear free energy relationship The demonstration of a linear free energy relationship by this means is not necessary for chemical systems because these usually involve substituent change directly adjacent to the reaction centre the correlation is thus chemically reasonable. Application of Equation (29) is significant when the substituent changes may not be so obviously connected with the reaction centre as in the case of the effect of point mutation on conformational changes in enzymes. 

This chapter introduces a model for visualizing the changes that take place in a reaction mixture as a chemical reaction proceeds. The model describes the requirements that must be met before a reaction can occur, and explains why certain factors speed the reaction up or slow it down. It will help us understand why some chemical reactions are significantly reversible and why such reactions reach a dynamic equilibrium with equal rates of change in both directions. It will also allow us to explore the factors that can push a chemical equilibrium forward to create more desired products or backwards to minimize the formation of unwanted products. 

Nondestructive assay (NDA) for safeguards describes analytical techniques to measure, check, and verify the amount of nuclear material or of the elemental or isotopic concentration of an item without producing significant physical or chemical changes in the item. It allows inspectors to determine both the quantity and composition of nuclear material without ever sampling it directly. Ultimately, NDA techniques provide for the independent verification of the total amount of nuclear material held at a nuclear facility. The main nuclear materials of interest are uranium (U) and plutonium (Pu). Usually, no single measurement method can... 

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