Partition equilibrium

Partition equilibrium

The most common chemical equilibrium systems involve reactants and products in the same phase - either all gases or all solutions. However, it is also possible to get equilibria between substances in different phases, such as two liquids that do not mix (are immiscible).

For example, ammonia is soluble in both water and the organic solvent trichloromethane - two immiscible solvents. If ammonia is first dissolved in water, and then an equal volume of trichloromethane is added, and the two liquids shaken together, the following equilibrium is established:
Kc = [NH3 (CHCl3)] / [NH3 (aq)]

The equilibrium concentrations of ammonia in each layer can be established by titration with standard acid solution. It can thus be determined that Kc remains constant, with a value of 0.4 in this case.

This particular kind of equilibrium constant measures how a substance distributes or partitions itself between two immiscible solvents. It is called the partition coefficient or distribution coefficient.

Substances that are ionic or polar are more soluble in water than in non-polar organic solvents and vice-versa.

Partition equilibrium chromatography is a type of chromatography that is typically used in GC. The stationary phase is a high boiling liquid bonded to solid surface and the mobile phase is a gas.


Wikimedia Foundation. 2010.

Игры ⚽ Нужно решить контрольную?

Look at other dictionaries:

  • Equilibrium — is the condition of a system in which competing influences are balanced and it may refer to:cienceBiology* Equilibrioception, the sense of balance present in humans and animals * Homeostasis, the ability of an open system, especially living… …   Wikipedia

  • partition coefficient — n the ratio of the amounts of a substance distributed between two immiscible phases (as two liquids or a stationary and a mobile phase in chromatography) at equilibrium called also distribution coefficient * * * the ratio in which a given… …   Medical dictionary

  • partition coefficient — Equilibrium constant for the partitioning of a molecule between hydrophobic (oil) and hydrophilic (water) phases. A measure of the affinity of the molecule for hydrophobic environments, and thus, for example, a rough guide to the ease with which… …   Dictionary of molecular biology

  • Partition coefficient — In chemistry and the pharmaceutical sciences, a partition (P) or distribution coefficient (D) is the ratio of concentrations of a compound in the two phases of a mixture of two immiscible solvents at equilibrium.[1] The terms gas/liquid partition …   Wikipedia

  • Partition function (statistical mechanics) — For other uses, see Partition function (disambiguation). Partition function describe the statistical properties of a system in thermodynamic equilibrium. It is a function of temperature and other parameters, such as the volume enclosing a gas.… …   Wikipedia

  • partition — par·ti·tion pär tish ən n the distribution of a substance between two immiscible phases in contact at equilibrium and esp. between two liquids partition vt * * * par·ti·tion (pahr tĭґshən) something that separates or divides into parts …   Medical dictionary

  • Correlated equilibrium — A solution concept in game theory Relationships Superset of Nash equilibrium Significance Proposed by …   Wikipedia

  • Dynamic equilibrium — For the economic concept, see Dynamic equilibrium (economics) A dynamic equilibrium exists once a reversible reaction ceases to change its ratio of reactants/products, but substances move between the chemicals at an equal rate, meaning there is… …   Wikipedia

  • Nonequilibrium partition identity — The nonequilibrium partition identity (NPI) is a remarkably simple and elegant[citation needed] consequence of the Fluctuation Theorem previously known as the Kawasaki Identity: (Carberry et al. 2004.) Thus in spite of the Second Law Inequality… …   Wikipedia

  • Chromatography — Pictured is a sophisticated gas chromatography system. This instrument records concentrations of acrylonitrile in the air at various points throughout the chemical laboratory. Chromatography (from Greek χρῶμα chroma color and γράφειν graphein to… …   Wikipedia

Share the article and excerpts

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