Qualitatively Interpreting the Equilibrium Constant

The Mond process for purifying nickel involves the formation of nickel tetracar-bonyl, Ni(CO)4, a volatile liqnid, from nickel metal and carbon monoxide. Carbon monoxide is passed over impnre nickel to form nickel carbonyl vapor, which, when heated, decomposes and deposits pnre nickel. 

In the preceding sections, we described how a chemical reaction reaches equilibrium and how you can characterize this equUihrium by the equilibrium constant. Now we want to see the ways in which an equiUbrium constant can be used to answer important questions. We will look at the following uses  

Qualitatively interpreting the equilibrium constant. By merely looking at the magnitude of K, you can teU whether a particular equilibrium favors products or reactants. 

Predicting the direction of reaction. Consider a reaction mixture that is not at equi-hbrium. By substituting the concentrations of substances that exist in a reaction mixture into an expression similar to the equihbrium constant and comparing with K, you can predict whether the reaction will proceed toward products or toward reactants (as defined by the way you write the chemical equation). 

Calculating equilibrium concentrations. Once you know the value of for a reaction, you can determine the composition at equilibrium for any set of starting concentrations. 

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Qualitative Interpretation of the Reaction Quotient, Q and the Equilibrium Constant, K... 

Applications of NMR spectroscopy to structural, thermodynamic, and dynamic processes have been described. A brief discussion of the types of problems appropriate for study by this technique has been included. H and 13C NMR spectroscopy has been applied to define the ligand coordination in complexes. These experiments, combined with 170-labeling experiments, allowed deduction of the coordination number of the vanadium atom. Integration of NMR spectra allowed measurement of the formation constants and equilibrium constants. 2D 13C and 51V EXSY experiments were used in a qualitative and quantitative manner to examine intra- and intermolecular dynamic processes, of which several examples are discussed. The interpretation of the rate matrix and its relationship to the chemical processes under examination were also described. 2D EXSY spectroscopy has great potential as a tool with which to probe mechanisms in complex reactions however, such uses often requires estimation of errors. The major source of error in 2D 51V EXSY NMR studies on a two- and four-site vanadate system were found to be baseline distortion and the errors were estimated. Our results suggest... 

However, if we wish to use Equation (137) to calculate this equilibrium constant it is clear that the appropriate frequencies to use are not those of the isolated species, but rather those of the strongly hydrogen-bonded system which actually exists in aqueous solution. A quantitative treatment is thus very difficult, but some qualitative interpretations are possible. 

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