Equilibrium and Energy

A rigorous treatment of chemical thermodynamics is beyond the scope of this book. However, there are several thermodynamic relationships that can provide important insights, even if we resort to a few oversimplifications of thermodynamic concepts. In an overview of inorganic chemistry and its applications, it is more important to appreciate what thermodynamics can tell us than to worry about its rigor or theoretical significance. 

Perhaps the most important equation relates the thermodynamic equilibrium constant K° to the standard free energy change AG° of the reaction  

Activities, and hence K° values, are necessarily dimensionless quantities and are defined with reference to a convenient standard state. The standard state now universally adopted in the Systeme International d Unites (SI) is 

The last restriction explains the hypothetical standard concentration of 1 molal obviously, 1 mol kg is quite concentrated, and the standard state conditions are extrapolated from high dilution. Gas concentrations are conveniently expressed as partial pressures  

SO the standard state for a gaseous reactant is 1 bar partial pressure with (extrapolated) ideal behavior. 

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For every component, C in number, on every stage, N in number, there are material, equilibrium, and energy balances, and the requirement that the mol fractions of liquid and vapor phases on each tray sum to unity. The four sets of these equations are ... 

Numerous physical transformations can be considered as a system changes from one energy state to another. Chemical reactions also involve reactants and products that have different energies. As a result, it is important to understand the relationship between equilibrium and energy. 

Figure 8-7 Graphical solution of equilibrium and energy balance equations to obtain adiabatic temperature and equilibrium conversion.

Module 5 Chemical Reactions, Equilibrium and Energy Changes... 

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