Properties Relative to Ideal Gases

One strategy, and one much used in thermod)mamics, divides a property F into two parts an ideal contribution, F j, and a deviation or correction term, F,j. This strategy can be realized in at least two ways. In the first, the deviation takes the form 

While in the second, the deviation takes the form of a ratio measure, 

In both ways the ideal substance must be well defined and its properties must be easy to compute beyond that, the choice of ideality is made strictly for convenience. In both approaches the job of computing the property F is reduced to the (hopefully) easier job of computing one of the deviation terms, either F, g or.  

Of the many measurables that exist, the ones whose values can be determined most readily are temperature, pressure, volume, and heat capacities. Of the many substances that exist, the ones whose measurables are most easily related to conceptuals are the substances that obey the ideal-gas equation of state. Therefore, the ideal gas 

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