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Raoult's law (/ ˈ r ɑː uː l z / law) is a relation of physical chemistry, with implications in thermodynamics.Proposed by French chemist François-Marie Raoult in 1887, [1] [2] it states that the partial pressure of each component of an ideal mixture of liquids is equal to the vapor pressure of the pure component (liquid or solid) multiplied by its mole fraction in the mixture.
The VLE concentration data can be determined experimentally or approximated with the help of theories such as Raoult's law, Dalton's law, and Henry's law. Such vapor–liquid equilibrium information is useful in designing columns for distillation, especially fractional distillation, which is a particular specialty of chemical engineers.
A McCabe–Thiele diagram for the distillation of a binary (two-component) feed is constructed using the vapor-liquid equilibrium (VLE) data—which is how vapor is concentrated when in contact with its liquid form—for the component with the lower boiling point. Figure 1: Typical McCabe–Thiele diagram for distillation of a binary feed
Vapor pressure of liquid and solid benzene. Equilibrium vapor pressure can be defined as the pressure reached when a condensed phase is in equilibrium with its own vapor. In the case of an equilibrium solid, such as a crystal, this can be defined as the pressure when the rate of sublimation of a solid matches the rate of deposition of its vapor ...
In thermodynamics, an activity coefficient is a factor used to account for deviation of a mixture of chemical substances from ideal behaviour. [1] In an ideal mixture, the microscopic interactions between each pair of chemical species are the same (or macroscopically equivalent, the enthalpy change of solution and volume variation in mixing is zero) and, as a result, properties of the mixtures ...
At the lower freezing point, the vapor pressure of the liquid is equal to the vapor pressure of the corresponding solid, and the chemical potentials of the two phases are equal as well. The equality of chemical potentials permits the evaluation of the cryoscopic constant as K f = R M T f 2 / Δ f u s H {\displaystyle K_{f}=RMT_{f}^{2}/\Delta ...
K is the distribution coefficient or K factor, defined as the ratio of mole fraction in the vapor phase () to the mole fraction in the liquid phase () at equilibrium. When Raoult's law and Dalton's law hold for the mixture, the K factor is defined as the ratio of the vapor pressure to the total pressure of the system: [1]
= the vapor–liquid equilibrium concentration of component in the liquid phase ( y / x ) {\displaystyle (y/x)} = Henry's law constant (also called the K value or vapor-liquid distribution ratio ) of a component