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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 fugacity of a condensed phase (liquid or solid) is defined the same way as for a gas: = and = It is difficult to measure fugacity in a condensed phase directly; but if the condensed phase is saturated (in equilibrium with the vapor phase), the chemical potentials of the two phases are equal (μ c = μ g).
Köhler theory combines the Kelvin effect, which describes the change in vapor pressure due to a curved surface, with Raoult's Law, which relates the vapor pressure to the solute concentration. [1] [2] [3] It was initially published in 1936 by Hilding Köhler, Professor of Meteorology in the Uppsala University.
Raoult's law states that for components 1, 2, etc. in a mixture: =, =, where P 1 °, P 2 °, etc. are the vapor pressures of components 1, 2, etc. when they are pure, and x 1, x 2, etc. are mole fractions of the corresponding component in the liquid.
This means that, at least at low concentrations, the vapor pressure of the solvent will be greater than that predicted by Raoult's law. For instance, for solutions of magnesium chloride , the vapor pressure is slightly greater than that predicted by Raoult's law up to a concentration of 0.7 mol/kg, after which the vapor pressure is lower than ...
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 ...
[1] [2] [3] A more fundamental statement was later labelled as the zeroth law after the first three laws had been established. The zeroth law of thermodynamics defines thermal equilibrium and forms a basis for the definition of temperature: if two systems are each in thermal equilibrium with a third system, then they are in thermal equilibrium ...
These are analogous to Boyle's law and Charles's law for gases. Similarly, the combined ideal gas law , P V = n R T {\displaystyle PV=nRT} , has as an analogue for ideal solutions Π V = n R T i {\displaystyle \Pi V=nRTi} , where Π {\displaystyle \Pi } is osmotic pressure; V is the volume; n is the number of moles of solute; R is the molar gas ...