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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).
The simplest definition is that an ideal solution is a solution for which each component obeys Raoult's law = for all compositions. Here p i {\displaystyle p_{i}} is the vapor pressure of component i {\displaystyle i} above the solution, x i {\displaystyle x_{i}} is its mole fraction and p i ∗ {\displaystyle p_{i}^{*}} is the vapor pressure ...
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 ...
In both cases, the explanation depends on the fact that many solutes are only present in the liquid phase and do not enter into the gas phase (except at extremely high temperatures). The vapor pressure affects the solute shown by Raoult's Law while the free energy change and chemical potential are shown by Gibbs free energy.
The temperature throughout the plot is assumed to be constant. The center trace is a straight line, which is what Raoult's law predicts for an ideal mixture. In general solely mixtures of chemically similar solvents, such as n-hexane with n-heptane, form nearly ideal mixtures that come close to obeying Raoult's law. The top trace illustrates a ...
The equilibrium concentration of each component in the liquid phase is often different from its concentration (or vapor pressure) in the vapor phase, but there is a relationship. 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.
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.