Introduction

More than one phases coexist at the same temperature and pressure.

K-Values

K-values is a phase-equilibrium ratio, for vapor-liquid systems,

${\displaystyle K_{i}=y_{i}/x_{i}}$

${\displaystyle y_{i}}$ is the mole fraction of a species in vapor phase, and ${\displaystyle x_{i}}$ is the mole fraction of a species in liquid phase.

For ideal solutions,

${\displaystyle K_{i}=P_{i}^{S}/P}$

K-values can be used for calculating bubble and dew points.

Reference

Seader, J. D., and Ernest J. Henley. Separation Process Principles. Hoboken, NJ: Wiley, 2006. Print.