Fugacity

Fugacity deals with the pressure of real gas and it is a chemical quantity, whose units are in terms of pressure. It is possible to determine the fugacity of gasses experimentally. On the other hand, the fugacity for different models including the ‘Van der Waals gas’ can be estimated. The fugacity coefficient, which is dimensionless, brings up the relation between the fugacity and the pressure of the ideal gas. The co efficient of fugacity is denoted by  and it is given by f/p.

As we know, the concentration of vapor as well as the gas will be commonly described by means of partial pressure. Hence, the concentrations of the real gases can be easily determined with the help of fugacity. Therefore, the concentration levels in the gasses can be easily modified with the help of fugacity coefficient just like the activity coefficients do in case of modifying condensed state concentrations. However, there is a relation between the condensed state and fugacity as well. When pressure has a significant role in any condition, then there is no doubt that the fugacity will have an equal important role in the same condition.

It is said that the derivation of the word called ‘fugacity’ is done from a well known language called Latin. The man who introduced the fugacity concept is Gilbert N. Lewis, who is one of the most appreciated chemists of United States.

Fugacity is very much helpful in better approximation when it comes to the real world gases pressure. Fugacity will be better to use when compared to the laws of ideal gas. On the other hand, while using fugacity, you can also make use of idealized system based relationships as well. Hence, there is nothing to be surprised when you find fugacity being employed in many fields including chemistry and engineering.

Questions:

• What is fugacity?
• Who introduced the concept of fugacity?