What is the Difference Between Activity and Fugacity?

Activity and fugacity are both concepts related to the non-ideal behavior of real gases in thermodynamics. The key difference between them lies in their definitions and the way they are used in chemical calculations.

• Activity refers to the effective concentration of a chemical species under non-ideal conditions. It is a measure of the relative amount of a substance in a mixture, taking into account the non-ideal behavior of real molecules.
• Fugacity, on the other hand, refers to the effective partial pressure of a chemical species under non-ideal conditions. It is a measure of the pressure that a real gas would exert if it were to behave like an ideal gas.

The relationship between activity and fugacity can be given as: activity = fugacity / pressure. In other words, the activity of a substance is equal to its fugacity divided by the pressure it exerts.

In summary, activity is a measure of the effective concentration of real molecules, while fugacity is a measure of the effective partial pressure of real gases. Both concepts are important in chemical thermodynamics for understanding the behavior of real gases under non-ideal conditions.

Comparative Table: Activity vs Fugacity

Activity and fugacity are both concepts related to the behavior of chemical species in a system, but they have distinct meanings and applications. Here is a table summarizing the differences between activity and fugacity:

In summary, activity is a measure of the effective concentration of a chemical species in a solution or mixture, while fugacity is a measure of the escaping tendency of a species from a solution or mixture. The choice between these two terms depends on the context in which they are being used.