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Topic: Dissociation (chemistry)

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  HighBeam Encyclopedia – Free Online Encyclopedia for Reference, Research, Facts
amphoterism in chemistry, the property of certain substances of acting either as acids or as bases depending on the reaction in which they are involved.
atomic mass unit or amu, in chemistry and physics, unit defined as exactly 1/12 the mass of an atom of carbon-12, the isotope of carbon with six protons and six neutrons in its nucleus.
inorganic chemistry the study of all the elements and their compounds with the exception of carbon and its compounds, which fall under the category of organic chemistry.
www.encyclopedia.com /category/Science_and_Technology/Chemistry/chem.html   (4304 words)

 Dissociation Summary
Dissociation may be accomplished by the addition of energy, as in the case of gaseous molecules dissociated by heat; or by the action of a solvent on a polar compound (i.e., electrolytic decomposition).
Dissociation is a psychological state or condition in which certain thoughts, emotions, sensations, or memories are separated from the rest of the psyche.
Attention to dissociation as a clinical feature is growing in recent years as a concommitant to knowledge of post-traumatic stress disorder, and as neuroimaging research and population studies show its relevance.
www.bookrags.com /Dissociation   (1797 words)

 AllRefer.com - dissociation (Chemistry) - Encyclopedia
Electrolytic dissociation occurs when an electrolyte is dissolved in a polar solvent.
Dissociation is generally reversible; when the atoms or ions of the dissociated substance are returned to the original conditions, they recombine in the original form of the substance.
The dissociation constant is a measure of the extent of dissociation.
reference.allrefer.com /encyclopedia/D/dissocia.html   (279 words)

 dissociation - HighBeam Encyclopedia
Measurement of the dynamic rates of association and dissociation of EGF with its cell-surface receptor in intact cells.
The oxyhemoglobin dissociation curve in liver cirrhosis *.
Pathological and nonpathological dissociation: the relevance of childhood trauma.
www.encyclopedia.com /doc/1E1-dissocia.html   (750 words)

 Dissociation (chemistry) - Search Results - MSN Encarta
Dissociation (chemistry), breaking up of compounds into simpler forms through a reversible reaction, especially under the influence of heat and of...
Dissociative Disorders, mental illnesses characterized by dissociation, a failure to integrate information about one’s personal identity, memories,...
Chemistry, History of : pictures related to the history of chemistry
encarta.msn.com /Dissociation_(chemistry).html   (144 words)

 Prof. Butler - Chemistry Department - University of Chicago
S, we used the technique of emission spectroscopy of dissociating molecules to investigate the dynamics which occurs during the subpicosecond dissociation event, providing a key link between the absorption spectrum and the final product quantum states.
We have recently introduced a method for investigating the competing unimolecular dissociation channels of isomerically-selected radicals as a function of internal energy in the radical.
Dissociation Dynamics of CH SH at 222, 248, and 193 nm ­ An Analog for Probing Nonadiabaticity in the Transition-State Region of Bimolecular Reactions, J.
chemistry.uchicago.edu /fac/butler.shtml   (730 words)

 FUNDAMENTAL CHALLENGES IN ELECTRON-DRIVEN CHEMISTRY   (Site not responding. Last check: 2007-09-18)
Only the rudiments of those dissociative collisions are understood, and it is not an exaggeration to state that it is currently beyond the state of the art to predict the branching ratios of the fragments and their excited states.
Thus electron impact can excite any dissociative state of a molecule and reduce it to fragments, and this is a key mechanism by which radicals and molecular fragments are produced in situations ranging from planetary atmospheres to molecular beam sources for experiments in molecular collisions.
Dissociative electron attachment is perhaps the best characterized electron interaction with many of the molecular systems pertinent to plasma processing and is the subject of considerable theoretical effort.
www.lbl.gov /ICSD/mccurdy/workshop_final_1.html   (9124 words)

 Frontiers of Interfacial Water Research Workshop
Understanding the chemistry of the aqueous solution-solid interface is fundamental to the development of new technologies for the treatment of contaminated water.
In general, the physical chemistry of organic-water interactions is fairly well understood, as are the physics and thermodynamics of water, ions, and electrolyte solutions.
The physical chemistry and transport of associated water shells with the electrolyte ion is poorly understood.
www.sandia.gov /water/waterworkshop/summaries.htm   (3533 words)

Analytical Chemistry · Biophysical Chemistry · Molecular Structure and Dynamics -- The structure and reactivity of biomolecules and biomolecule/water interactions are investigated using sophisticated new methods in mass spectrometry, separations, and spectroscopy.
The Williamsí group is developing dissociation methods, including photodissociation and flbody infrared radiative dissociation, for rapid identification and sequencing of large protein and DNA molecules.
These interactions also result in unusual ion-molecule charge-transfer and dissociation chemistry that is being explored by experimental methods and by molecular dynamics simulations.
chem.berkeley.edu /people/faculty/williams/williams.html   (385 words)

 CIRL - Pioneers in Electricity and Magnetism: Svante Arrhenius
The award for chemistry was bestowed to him in honor of his theory of electrolytic dissociation, though in its incipient form, which appeared in his doctoral dissertation, the theory was poorly received by his professors.
Based upon his investigations on the conductivity of electrolytes, Arrhenius was convinced that when an electrolyte is dissolved in water, it dissociates to some degree into positive and negative ions, and that the extent of dissociation depends upon the nature of the electrolyte and its level of concentration (dissociation being greater in dilute solutions).
According to Arrhenius, an acid is a substance that, when it dissociates in water, yields hydrogen ions (H+), whereas the dissociation of a base in water yields hydroxide ions (OH-).
www.magnet.fsu.edu /education/tutorials/pioneers/arrhenius.html   (988 words)

 Dissociation and Ionization   (Site not responding. Last check: 2007-09-18)
I thought it was that ionization involved a reaction with water to produce ions whereas dissociation involved an ionic substance simply separating into the ions of which it is made.
The equilibrium constant for such reactions, unfortunately, is sometimes referred to as the "dissociation" constant, which strictly speaking is incorrect -- the proper term being "ionization" constant.
Finally, an ionic dissociation reaction in water might be the dissolution of an ionic solid: NaCl(s) -----> Na+(aq) + Cl- (aq) This does not involve any subsequent reactions of the ions produced with water.
www.newton.dep.anl.gov /askasci/chem03/chem03128.htm   (406 words)

The dissociation of an arrehnius acid commonly pertains to the acid in water.
There are two basic factors in the degree of dissociation of a proton-the bond dissociation energy and the degree of polarity.
Yes, water helps in the dissociation of a proton and formation of other ions but the oxygen being more electronegative is not a factor.
www.physicsforums.com /showthread.php?t=13683   (874 words)

 Dissociation (chemistry) - Wikipedia, the free encyclopedia
Dissociation in chemistry and biochemistry is a general process in which complexes, molecules, or salts separate or split into smaller molecules, ions, or radicals, usually in a reversible manner.
Dissociation is the opposite of association and recombination.
The dissociation of salts by solvation in a solution like water means the separation of the anions and cations.
en.wikipedia.org /wiki/Dissociation_(chemistry)   (190 words)

 College Chemistry: Acids and Bases
If you are learning chemistry now, the Chemistry Tips Daily is for you--it is a one minute learning each day to the chemistry mastery, free for all students.
The equilibrium constant for the acid dissociation reaction ´ the base dissociation constant for the conjugate base = the water dissociation constant at that temperature.
Therefore, the concentration of the original strong acid or base is assumed to equal the concentration of the hydrogen or hydroxide ion.
www.chemistry24.com /college_chemistry/acids-and-bases.html   (594 words)

 ChemTeam: Bjerrum and Strong Electrolytes
The fact that the so-called "degree of dissociation" depends upon the electric constants of the substances without admitting of any specific influence by chemical affinity becomes quite natural when this quantity in reality is the decrease in electrolytic friction due to the electric forces among the ions.
In the case of the dissociation of weak electrolytes, as is well known, the law of mass action has been found to be applicable, but by means of the conductivity we here measure a real dissociation, since the ion-concentration in the solution is so small that we can consider the electrolytic friction as constant.
The only thing that is not explained so well by the new as by the old theory is the agreement between the decrease in the molecular conductivity and the decrease in the molecular depression of the freezing-point with the increase in concentration.
dbhs.wvusd.k12.ca.us /webdocs/Chem-History/Bjerrum-Strong-Electrolyte.html   (524 words)

 Research Interests   (Site not responding. Last check: 2007-09-18)
Emphasis is placed in the areas of gas-phase ion chemistry and instrumentation for organic and biological mass spectrometry.
Fundamental aspects of ionization, unimolecular reactions, and bi-molecular reactions are studied with the goal of improving the capabilities of analytical mass spectrometry.
Current projects include, for example, the application of electrospray and ion/ion chemistry to the rapid sequencing of DNA, the study of the dissociation chemistry of multiply-charged macro-ions, and the combination of ion/ion chemistry and unimolecular dissociation chemistry for the rapid identification of proteins in complex mixtures.
www.chem.purdue.edu /mcluckey/SAMresearchinterests.html   (289 words)

 Dissociation and Ionization   (Site not responding. Last check: 2007-09-18)
Dissociation refers to the breaking of a chemical bond without reference to whether the products are ions or neutral fragments.
However, ionization is a general term which refers to the formation of ions, and not necessarily from dissociation.
Dissociation is when a single particle becomes two or more.
www.newton.dep.anl.gov /askasci/chem00/chem00929.htm   (289 words)

 Drug Pathways and Chemical Concepts- 8. Dissociation Constant
It is a numeric representative of the relative proton transfer for that substance, or the likelihood of that compound donating a proton.
This dissociation constant is an important characteristic of drug molecules, and provides a tool to anticipate some of the "behaviors" of that compound.
Dissociation constants are determined by experimental data, and are unique to each molecule.
science.kennesaw.edu /~mhermes/pheno/pheno08.htm   (942 words)

 Course Descriptions for Chemistry and Biochemistry, SUNY College of Environmental Science and Forestry
This first semester general chemistry course is organized around the physical and chemical properties of matter.
The second course in general chemistry continues the development of chemical reactivity by focusing on chemical kinetics and chemical equilibrium.
The chemistry of the systems discussed will be stressed as well as the important physical aspects.
www.esf.edu /chemistry/courses.htm   (1593 words)

 A P P E N D I C E S
An acid salt is a compound derived from a polyprotic acid where at least one of the acid hydrogen atoms in the acid molecule is replaced by a metal, while some ‘acid’ hydrogen still remains, eg.
The enthalpy increase that accompanies the homolytic fission of one mole of bonds in a covalently bonded species, to give individual atoms and/or radicals, with both the original species and the resulting fragments being in their standard states, and at standard temperature and pressure.
A term that is used loosely to indicate bond enthalpies: the larger the bond enthalpy, the greater the strength of the bond.
www.uwcsea.edu.sg /chem/IBfolder/IBGlossary.html   (4805 words)

 IB Chemistry glossary of terms and definitions   (Site not responding. Last check: 2007-09-18)
The enthalpy increase that accompanies the homolytic fission of one mole of bonds in a covalently bonded species, to give individual atoms and/or radicals, with both the original species and the resulting fragments being in their standard states, and at standard temperature and pressure.
The enthalpy increase that accompanies the homolytic fission of one mole of bonds in a covalently bonded species, to give individual atoms and/or radicals, with both the original species and the resulting fragments being in their standard states, and at stand temperature and pressure.
A term that is used loosely to indicate bond enthalpies: the larger the bond enthalpy, the greater the strength of the bond.
ibchem.com /root_htm/defn/IBgloss.htm   (4871 words)

 From TNT to BTX to DNA
In tandem mass spectrometry, the ions produced by the glow discharge source, often referred to as parent ions, are mass-selected and caused to dissociate prior to a second stage of mass analysis.
Having studied the ion chemistry and optimized conditions for ionizing hydrocarbons in the complex matrix of engine exhaust, we faced the challenge of performing tandem mass spectrometry in sufficiently rapid fashion to satisfy the time requirements of the measurement.
His research interests are in the areas of gas-phase ion chemistry and instrumentation for organic and biological mass spectrometry.
www.ornl.gov /info/ornlreview/measure/analy/fromtnt/tnt.htm   (4487 words)

 Prof. Mazziotti - Chemistry Department - University of Chicago
Advancement in reduced-density-matrix theory is fostering the development of a new paradigm in theoretical chemistry that promises to promote unprecedented growth in our ability to explore computationally a myriad of chemical questions from structure to reactivity.
The new methodology is not limited to electronic structure but rather is also appropriate for other aspects of chemistry including the prediction of vibrational and rotational molecular properties.
While both Hartree-Fock and density functional theory work within the framework of a single electron, the importance of the electron pairing in the chemical bond is well-known to every chemist.
chemistry.uchicago.edu /fac/mazziotti.shtml   (694 words)

 Laser Induced Chemistry at BNL
Two programs in the Chemistry Department performed research in this field: one group evolved naturally from the group previously studying isotope effects; the second group represented growth in the Chemistry Department in a new direction.
P atoms revealed that at most 30% of the observed rate was due to reaction enhanced by vibrational excitation of the ozone.
This process was shown to proceed by dissociation into SF and a fluorine atom, which then reacted with a hydrogen-containing molecule to form hydrogen fluoride.
www.bnl.gov /chemistry/History/LaserInducedChemistry.asp   (777 words)

This work is interdisciplinary and performed by both Analytical Chemistry and Chemical Biology graduate students as well as postdoctoral researchers with expertise in Physical and Inorganic Chemistry.
In research funded by the American Society for Mass Spectrometry, the Petroleum Research Fund, and the National Science Foundation, we are characterizing and applying ECD and EDD in a Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometer to the structural characterization of nucleic acids and their complexes with small molecules.
We are exploring the utility of the latter characteristic for elucidation of nucleic acid structure and folding.
www.umich.edu /~fticrms/Research.htm   (676 words)

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