Printer Friendly
Dictionary, Encyclopedia and Thesaurus - The Free Dictionary
1,775,474,549 visitors served.
forum mailing list For webmasters
?
New: Language forums
Dictionary/
thesaurus
Medical
dictionary
Legal
dictionary
Financial
dictionary
Acronyms
 
Idioms
Encyclopedia
Wikipedia
encyclopedia
?

Raoult's law
(redirected from Vapor pressure lowering)

   Also found in: Medical, Wikipedia 0.01 sec.
Raoult's law (rälz`) [for F. M. Raoult, a French physicist and chemist] states that the addition of solute to a liquid lessens the tendency for the liquid to become a solid or a gas, i.e., reduces the freezing point and the vapor pressure vapor pressure, pressure exerted by a vapor that is in equilibrium with its liquid. A liquid standing in a sealed beaker is actually a dynamic system: some molecules of the liquid are evaporating to form vapor and some molecules of vapor are condensing to form liquid.
..... Click the link for more information.
 (see solution solution, in chemistry, homogeneous mixture of two or more substances. The dissolving medium is called the solvent , and the dissolved material is called the solute. A solution is distinct from a colloid or a suspension .
..... Click the link for more information.
). For example, the addition of salt to water causes the water to freeze below its normal freezing point (0°C;) and to boil above its normal boiling point (100°C;). Qualitatively, depression of the freezing point and reduction of the vapor pressure are due to a lowering of the concentration of water molecules, since the more solute is added, the less the percentage of water molecules in the solution as a whole and therefore the less their tendency to form into a crystal solid or to escape as a gas. Quantitatively, Raoult's law states that the solvent's vapor pressure in solution is equal to its mole mole, in chemistry, a quantity of particles of any type equal to Avogadro's number, or 6.02×1023 particles. One gram-molecular weight of any molecular substance contains exactly one mole of molecules.
..... Click the link for more information.
 fraction times its vapor pressure as a pure liquid, from which it follows that the freezing point depression and boiling point elevation are directly proportional to the molality of the solute, although the constants of proportion are different in each case. This mathematical relation, however, is accurate only for dilute solutions. The fact that an appropriate solute can both lower the freezing point and raise the boiling point of a pure liquid is the basis for year-round antifreeze for automobile cooling systems. In the winter the antifreeze lowers the freezing point of the water, preventing it from freezing at its normal freezing point; in the summer it guards against boilover by raising the boiling point of the water.
Raoult's law [rä′ülz ‚lȯ]
(physical chemistry)
The law that the vapor pressure of a solution equals the product of the vapor pressure of the pure solvent and the mole fraction of solvent.


How to thank TFD for its existence? Tell a friend about us, add a link to this page, add the site to iGoogle, or visit webmaster's page for free fun content.
?Page tools
Printer friendly
Cite / link
Email
Feedback
? Mentioned in
 
Encyclopedia browser? ? Full browser
 
 
Encyclopedia
?

Disclaimer | Privacy policy | Feedback | Copyright © 2009 Farlex, Inc.
All content on this website, including dictionary, thesaurus, literature, geography, and other reference data is for informational purposes only. This information should not be considered complete, up to date, and is not intended to be used in place of a visit, consultation, or advice of a legal, medical, or any other professional. Terms of Use.