en>Makyen: /* References */Fix various citation "unknown parameter", ISBN, and URL errors/issues. Replace hard space with   throughout per WP:NBSP. Run gen fixes and typos if found. using AWB

2014-04-23T11:42:18Z

References: Fix various citation "unknown parameter", ISBN, and URL errors/issues. Replace hard space with   throughout per WP:NBSP. Run gen fixes and typos if found. using AWB

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en>Incnis Mrsi: image, better lead and general cleanup; see WP: MOSPHYS (currently a draft, not an official guideline)

2013-02-10T10:08:03Z

image, better lead and general cleanup; see WP: MOSPHYS (currently a draft, not an official guideline)

← Older revision		Revision as of 12:08, 10 February 2013
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	~~I woke up another day~~ and ~~realized - I~~'~~ve been single for some time today~~ and ~~following much intimidation from pals I today locate myself opted for web dating~~. ~~They guaranteed me that there are~~ a the ~~today show luke bryan (~~[~~http~~://~~lukebryantickets~~.~~flicense~~.~~com http~~://~~lukebryantickets~~.~~flicense~~.~~com~~]~~) lot~~ of ~~pleasant~~, ~~standard~~ and ~~interesting visitors to meet up~~, ~~so here goes~~ the ~~toss!~~<br>~~I endeavor to keep~~ as ~~physically fit~~ as ~~potential being at~~ the ~~gymnasium many times~~ a ~~week~~. ~~I love my athletics~~ and ~~[http:~~//~~Answers~~.~~Yahoo~~.~~com/search/search_result?p~~=~~endeavor&submit-go~~=~~Search+Y!+Answers endeavor~~] to ~~play or watch since many a possible~~. ~~Being winter I shall often at~~ [~~http:~~//~~www.hotelsedinburgh.org luke bryan concert tour 2014~~] ~~Hawthorn matches~~. ~~Note~~: ~~In case that you would contemplated purchasing a sport I really don't brain, I have noticed~~ the ~~carnage~~ of ~~wrestling fits~~ at ~~stocktake sales~~.<br>~~My fam~~ and ~~friends are magnificent~~ and ~~hanging out~~ with ~~them at tavern gigs or dishes~~ is ~~definitely a necessity~~. ~~I haven~~'~~t ever been in~~ to ~~[http:~~//~~Imgur~~.~~com~~/~~hot?q=nightclubs nightclubs~~] ~~as I find you~~ [~~http~~://~~minioasis~~.~~com meet and greet luke bryan tickets~~] ~~could do not get~~ a ~~decent dialog against the sound~~. ~~I likewise have two quite adorable and unquestionably cheeky canines who~~ are ~~almost always enthusiastic~~ to ~~meet up new people~~.<br><br><br><br>~~Here is my web blog~~: [~~http~~:~~//www.banburycrossonline.com vip tickets luke bryan~~]		{{For\|\|Dissociation (disambiguation){{!}}Dissociation}}
			{{Unreferenced\|date=December 2009}}
			'''Dissociation''' in chemistry and [[biochemistry]] is a general process in which ionic compounds ([[Complex (chemistry)\|complexes]], or [[salts]]) separate or split into smaller particles, ions, or [[Radical (chemistry)\|radicals]], usually in a reversible manner. For instance, when a [[Brønsted-Lowry]] [[acid]] is put in water, a [[covalent]] bond between an [[electronegative]] atom and a hydrogen atom is broken by [[heterolytic fission]], which gives a proton and a negative [[ion]]. Dissociation is the opposite of '''association''' and '''recombination'''. The process is frequently confused with [[ionization]].

			== Dissociation constant ==
			For reversible dissociations in a [[chemical equilibrium]]
			: AB {{Eqm}} A + B
			the [[dissociation constant]] ''K''<sub>a</sub> is the ratio of dissociated to undissociated compound
			: <math>K_a = \mathrm{\frac{[A][B]}{[AB]}}</math>
			where the brackets denote the equilibrium concentrations of the species.

			== Dissociation degree ==

			The dissociation degree is the fraction of original solute molecules that have dissociated. It is usually indicated by the Greek symbol <math> \alpha </math>. More accurately, degree of dissociation refers to the amount of solute dissociated into ions or radicals per mole. In case of very strong acids and bases, degree of dissociation will be close to 1. Less powerful acids and bases will have lesser degree of dissociation. There is a simple relationship between this parameter and the [[van 't Hoff factor]] '''<math> i </math>'''. If the solute substance dissociates into <math> n </math> ions, then

			:::<math> i = 1 + \alpha (n - 1) </math>

			For instance, for the following dissociation

			:::KCl {{Eqm}} K<sup>+</sup> + Cl<sup>-</sup>

			As <math> n = 2 </math>, we would have that <math> i = 1 + \alpha </math>

			== Salts ==
			The dissociation of salts by [[solvation]] in a [[solution]] like [[water (molecule)\|water]] means the separation of the [[anion]]s and [[cation]]s. The salt can be recovered by [[evaporation]] of the solvent. See also: [[Solubility equilibrium]]

			An electrolyte refers to a substance that contains free ions and can be used as an electrically conductive medium. Most of the solute does not dissociate in a weak electrolyte whereas in a strong electrolyte a higher ratio of solute dissociates to form free ions.

			A weak electrolyte is a substance whose solute exists in solution mostly in the form of molecules, with only a small fraction in the form of ions. Simply because a substance does not readily dissolve does not make it a weak electrolyte. [[Acetic acid]] (CH<sub>3</sub>COOH) and [[ammonium]] (NH<sub>4</sub><sup>+</sup>) are good examples. Acetic acid is extremely soluble in water, but most of the compound dissolves into molecules, rendering it a weak electrolyte. Weak bases and weak acids are generally weak electrolytes. In an aqueous solution there will be some CH<sub>3</sub>COOH and some CH<sub>3</sub>COO<sup>-</sup> and H<sup>+</sup>.

			A strong electrolyte is a solute that exists in solution completely or nearly completely as ions. Again, the strength of an electrolyte is defined as the percentage of solute that is ions, rather than molecules. The higher the percentage, the stronger the electrolyte. Thus, even if a substance is not very soluble, but does dissociate completely into ions, the substance is defined as a strong electrolyte. Similar logic applies to a weak electrolyte. Strong acids and bases are good examples such as HCl, H<sub>2</sub>SO<sub>4</sub>, NaCl. These will all exist as ions in an aqueous medium.

			== Gases ==
			The degree of dissociation in [[gases]] is denoted by the symbol α where α refers to the percentage of gas molecules which dissociate. Various relationships between K<sub>p</sub> and α exist depending on the stoichiometry of the equation. The example of [[dinitrogen tetroxide]] (N<sub>2</sub>O<sub>4</sub>) dissociating to [[nitrogen dioxide]] (NO<sub>2</sub>) will be taken.
			:N<sub>2</sub>O<sub>4</sub> {{Eqm}} 2NO<sub>2</sub>
			If the initial concentration of dinitrogen tetroxide is 1 mole per litre, this will decrease by α at equilibrium giving, by stoichiometry, 2α moles of NO<sub>2</sub>. The [[equilibrium constant]] (in terms of pressure) is given by the equation;

			<math>K_p = \mathrm{\frac{p(NO_2)^2}{p(N_2O_4)}}</math>

			Where p represents the partial pressure. Hence, through the definition of [[partial pressure]] and using p<sub>T</sub> to represent the total pressure and x to represent the mole fraction;

			<math>K_p =\mathrm{ \frac{(p_T)^2(x(NO_2))^2}{(p_T)(x(N_2O_4))} = \frac{(p_T)(x(NO_2))^2}{(x(N_2O_4))}}</math>

			The total number of moles at equilibrium is (1-α)+(2α) which is equivalent to 1+α. Thus, substituting the mole fractions with actual values in term of alpha and simplifying;

			<math>K_p = \frac{(\mathrm{p_T})(4\alpha^2)}{(1+\alpha)(1-\alpha)} = \frac{(\mathrm{p_T})(4\alpha^2)}{(1-\alpha^2)}</math>



			This equation is in accordance with Le Chatelier's Principle. ''K''<sub>p</sub> will remain constant with temperature. The addition of pressure to the system will increase the value of p<sub>T</sub> so α must decrease to keep ''K''<sub>p</sub> constant. In fact, increasing the pressure of the equilibrium favours a shift to the left favouring the formation of dinitrogen tetroxide (as on this side of the equilibrium there is less pressure since pressure is proportional to number of moles) hence decreasing the extent of dissociation α.

			== Acids ==
			The dissociation of acids in a solution means the split-off of a [[proton]] H<sup>+</sup>, see [[Acid-base reaction theories]]. This is an equilibrium process, meaning that dissociation and recombination takes place at the same time. The [[acid dissociation constant]] ''K''<sub>a</sub> is an indicator of the acid strength: stronger acids have a higher ''K''<sub>a</sub> value (and a lower p''K''<sub>a</sub> value).

			== Fragmentation ==
			[[Fragmentation (chemistry)\|Fragmentation]] of a molecule can take place by a process of [[Heterolysis (chemistry)\|heterolysis]] or [[homolysis (chemistry)\|homolysis]].

			== Receptors ==
			[[Receptor (biochemistry)\|Receptors]] are [[protein]]s that bind small [[ligands]]. The dissociation constant ''K''<sub>d</sub> is used as indicator of the [[Affinity (pharmacology)\|affinity]] of the ligand to the receptor. The higher the affinity of the ligand for the receptor the lower the ''K''<sub>d</sub> value (and the higher the p''K''<sub>d</sub> value).

			== See also ==
			* [[Ionization]]
			* [[Acid]]
			* [[Base (chemistry)]]
			* [[Thermal decomposition]]

			{{DEFAULTSORT:Dissociation (Chemistry)}}
			[[Category:Equilibrium chemistry]]
			[[Category:Chemical processes]]

en>Incnis Mrsi: rewording; some reasonings; more examples in chemistry

2012-08-19T16:30:01Z

rewording; some reasonings; more examples in chemistry

New page

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Energy level splitting - Revision history

en>Makyen: /* References */Fix various citation "unknown parameter", ISBN, and URL errors/issues. Replace hard space with &nbsp; throughout per WP:NBSP. Run gen fixes and typos if found. using AWB

en>Incnis Mrsi: image, better lead and general cleanup; see WP: MOSPHYS (currently a draft, not an official guideline)

en>Incnis Mrsi: rewording; some reasonings; more examples in chemistry

en>Makyen: /* References */Fix various citation "unknown parameter", ISBN, and URL errors/issues. Replace hard space with throughout per WP:NBSP. Run gen fixes and typos if found. using AWB