Real Gases—Ideal Gaseous Solutions

Understanding the choice of standard states in a problem is critical to proper treatment. Sometimes the standard state is one which does not exist at all, but can be readily pictured, hypothetically. For example, most gas mixtiu es do not behave in an ideal fashion. The molecules occupy space (they are not point molecules) they will interact to some extent unless they are infinitely far apart Hence, the commonly used standard state for gaseous substances is defined as hypothetical partial pressure of one atmosphere. Hypothetical, that is, because at one atmosphere, real gases will require some correction in their free energy value to compensate for their volumes and interactions. Analogously, the standard state for solutes commonly used is hypothetical one molal cMwcentration i.e., the concentration of an ideal solute in an ideal solution that would result in the value of the standard free energy. In real solutions, a correction would have to be... 

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