Volatility (chemistry)


Volatility (chemistry)

Volatility in the context of chemistry, physics and thermodynamics is a measure of the tendency of a substance to vaporize. It has also been defined as a measure of how readily a substance vaporizes. At a given temperature, substances with higher vapor pressures will vaporize more readily than substances with a lower vapor pressure. [ [http://www.bae.uky.edu/~snokes/BAE549thermo/gasesvapor.htm Gases and Vapor] (University of Kentucky website)] [ [http://www.coop.engr.uvic.ca/engrweb/whmis/terms.html#V Definition of Terms] (University of Victoria website)] [cite book|author=James G. Speight|title=The Chemistry and Technology of Petroleum|Edition=4th Edition|publisher=CRC Press|date=2006|id=ISBN 0-8493-9067-2] [cite book|author=Kister, Henry Z.|title=Distillation Design|edition=1st Edition|publisher=McGraw-hill|year=1992|id=ISBN 0-07-034909-6]

Although usually applying to liquids, volatility can apply to solid materials such as dry ice (solid carbon dioxide) and ammonium chloride, which can change directly from solid to vapor without becoming liquid. The direct transition of a solid to a vapor is called sublimation.

Relation between vapor pressures and normal boiling points of liquids

Vapor pressure is the pressure of a vapor which is in equilibrium with its non-vapor phases (i.e., liquid or solid). Most often the term is used to describe a liquid's tendency to evaporate. It is a measure of the tendency of molecules and atoms to escape from a liquid or a solid. A liquid's atmospheric pressure boiling point corresponds to the temperature at which its vapor pressure is equal to the surrounding atmospheric pressure and it is often called the normal boiling point.

The higher the vapor pressure of a liquid at a given temperature, the higher the volatility and the lower the normal boiling point of the liquid.

The vapor pressure chart to the right has graphs of the vapor pressures versus temperatures for a variety of liquids. [cite book|author=Perry, R.H. and Green, D.W. (Editors)|title=Perry's Chemical Engineers' Handbook|edition=7th Edition|publisher=McGraw-Hill|year=1997|id= ISBN 0-07-049841-5] As can be seen in the chart, the liquids with the highest vapor pressures have the lowest normal boiling points.

For example, at any given temperature, propane has the highest vapor pressure of any of the liquids in the chart. It also has the lowest normal boiling point(-43.7 °C), which is where the vapor pressure curve of propane (the purple line) intersects the horizontal pressure line of one atmosphere (atm) of absolute vapor pressure.

ee also

*Clausius-Clapeyron relation
*Distillation
*Fractional distillation
*Partial pressure
*Raoult's law
*Relative volatility
*Vapor-liquid equilibrium
*Vapor pressure

References

External links

* [http://www.ilpi.com/msds/ref/volatility.html Volatility from ilpi.com]
*


Wikimedia Foundation. 2010.

Look at other dictionaries:

  • Volatility — is the measure of the state of instability.*For volatility in chemistry, see Volatility (chemistry) *For volatility in finance, see Volatility (finance) *For the measure comparing the vapor pressures of the components in a liquid mixture of… …   Wikipedia

  • Relative volatility — is a measure comparing the vapor pressures of the components in a liquid mixture of chemicals. This quantity is widely used in designing large industrial distillation processes.cite book|author=Kister, Henry Z.|title=Distillation… …   Wikipedia

  • Inorganic chemistry — For the journal, see Inorganic Chemistry (journal). Inorganic compounds show rich variety: A: Diborane features unusual bonding B: Caesium chloride has an archetypal crystal structure C: Fp2 is an organometallic complex D …   Wikipedia

  • Organic chemistry — Structure of the methane molecule: the simplest hydrocarbon compound. Organic chemistry is a subdiscipline within chemistry involving the scientific study of the structure, properties, composition, reactions, and preparation (by synthesis or by… …   Wikipedia

  • Volatile — may refer to: Chemistry Volatility (chemistry), a measure of the tendency of a substance to vaporize Relative volatility, a measure of vapor pressures of the components in a liquid mixture Volatiles, a group of compounds with low boiling points… …   Wikipedia

  • Volatilidad (química) — La volatilidad en el contexto de la química, la física y la termodinámica es una medida de la tendencia de una sustancia a pasar a vapor. Se ha definido también como una medida de la facilidad con que una sustancia se evapora. A una temperatura… …   Wikipedia Español

  • Volatile organic compound — Volatile organic compounds (VOCs) are organic chemicals that have a high vapor pressure at ordinary, room temperature conditions. Their high vapor pressure results from a low boiling point, which causes large numbers of molecules to evaporate or… …   Wikipedia

  • Nobel Prizes — ▪ 2009 Introduction Prize for Peace       The 2008 Nobel Prize for Peace was awarded to Martti Ahtisaari, former president (1994–2000) of Finland, for his work over more than 30 years in settling international disputes, many involving ethnic,… …   Universalium

  • Сиджвик, Невил Винсент — В Википедии есть статьи о других людях с такой фамилией, см. Сиджвик. Невил Винсент Сиджвик Nevil Vincent Sidgwick Род деятельности: Химик Дата рождения: 8 мая …   Википедия

  • Gasoline — This article is about the fuel and industrial solvent. For other uses, see Gasoline (disambiguation). Petrol redirects here. For other uses, see Petrol (disambiguation). For the bird group, see petrel. A jar containing gasoline …   Wikipedia


Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”

We are using cookies for the best presentation of our site. Continuing to use this site, you agree with this.