partialmolvolum

Partialmolvolum refers to the partial molar volume of a component in a mixture. It is defined as the change in the total volume when an infinitesimal amount of that component is added to the system at constant temperature and pressure, with the amounts of all other components held fixed. The conventional symbol is V̄_i, and it is given by V̄_i = (∂V/∂n_i)_(T,P,n_j). For a multicomponent system, the volume change satisfies dV = ∑_i V̄_i dn_i.

Partialmolvolum depends on composition, temperature, and pressure, and it can be larger or smaller than the molar volume of the pure component, depending on molecular interactions and packing in the mixture. In an ideal solution, where volume is a linear combination of component volumes, V̄_i equals the molar volume of the pure component i. In real solutions, deviations occur and V̄_i can change as the solution is diluted or concentrated.

In practical terms, partialmolvolum is used to analyze solution thermodynamics and to interpret excess molar volumes, as well as to relate to other partial properties such as partial molar expansivity and partial molar compressibility. It is typically determined from density or pressure–volume–temperature data and incorporated into equations of state and activity models. In dilute solutions, the partialmolvolum of a solute tends toward a limiting value that reflects how the solvent environment accommodates the solute.