| Revision as of 08:31, 23 October 2017 edit132.68.135.93 (talk) →Ionic compounds← Previous edit | Latest revision as of 14:47, 14 July 2021 edit undoTom.Reding (talk | contribs)Autopatrolled, Extended confirmed users, Page movers, Template editors3,942,613 editsm +{{Authority control}} (1 ID from Wikidata), WP:GenFixes on (uncategorized page)Tag: AWB | ||
| (10 intermediate revisions by 7 users not shown) | |||
| Line 1: | Line 1: | ||
| #REDIRECT ] | |||
| {{merge|Solvation|discuss=Talk:Dissolution (chemistry)#Merger proposal|date=December 2016}} | |||
| {{multiple issues| | |||
| {{Refimprove science|date=December 2009}} | |||
| {{one source|date=June 2015}} | |||
| {{Expert needed|Chemistry|talk=Adding tags to indicate entirety of article unsourced or poorly sourced|reason=complete lack of expert content derived from secondary sources, and chosen with a broad scholarly view of the modern discipline|date=June 2015}} | |||
| {{Requires attention|for=repeated appearance of dubious, naive, and non-scholarly statements on the title subject|date=June 2015}} | |||
| }} | |||
| {{R with history}} | |||
| ] solution by dissolving ] (]) in ]. The salt is the solute and the water the solvent.]] | |||
| ], formerly dissolved in crystal of ], is left behind after the ] crystal of pyrite dissolved away. Note a corner of the former cube seen in center of rock.]] | |||
| The '''dissolution''' of gases, liquids, or solids into a liquid or other ] is a process by which these original states become solutes (dissolved components), forming a ] of the gas, liquid, or solid in the original solvent. ]s are the result of ''dissolution'' of one solid into another, and occur, e.g., in ]s, where their formation is governed and described by the relevant ]. In the case of a crystalline solid dissolving in a liquid, the crystalline structure must be disintegrated such that the separate atoms, ions, or molecules are released. For liquids and gases, the molecules must be able to form non-] ] with those of the solvent for a solution to form. | |||
| The ] of the overall, isolated process of dissolution must be negative for it to occur, where the component free energies contributing include those describing the disintegration of the associations holding the original solute components together, the original associations of the bulk solvent, and the old and new associations between the undissolved and dissolved materials.{{citation needed lead|date=June 2015}} | |||
| Dissolution is of fundamental importance in all chemical processes, natural and unnatural, from the decomposition of a dying organism and return of its chemical constituents into the ], to the laboratory testing of new, man-made soluble drugs, catalysts, etc.{{citation needed|date=June 2015}} Dissolution testing is widely used in industry, including in the pharmaceutical industry to prepare and ] chemical agents of consistent ] that will dissolve, optimally, in their target millieus as they were ]. | |||
| Some distinctions can be made between ]. | |||
| ==Dissolution by class of compound== | |||
| {{unreferenced section|date=June 2015}} | |||
| === Gases === | |||
| {{See also|Henry's law}} | |||
| Gaseous elements and compounds will dissolve in liquids dependent on the interaction of their bonds with the liquid solvent.{{dubious|date=June 2015}}{{citation needed|date=June 2015}} | |||
| === Liquids === | |||
| Gaseous elements and compounds may also dissolve in another liquid depending on the compatibility of the chemical and physical bonds in the substance with those of the solvent.{{dubious|date=June 2015}}{{citation needed|date=June 2015}} ]s play an important role in aqueous dissolution.{{citation needed|date=June 2015}} | |||
| === Ionic compounds === | |||
| For ]s, dissolution takes place when the ionic lattice breaks up and the separate ions are then solvated. This most commonly occurs in ]s, such as ] or ]: | |||
| :NaCl<sub>(s)</sub> → Na<sup>+</sup><sub>(aq)</sub> + Cl<sup>−</sup><sub>(aq)</sub> | |||
| In a colloidal dispersed system, small dispersed particles of the ionic lattice exist in equilibrium with the saturated solution of the ions, i.e. | |||
| :NaCl<sub>(aq)</sub> <math> \rightleftharpoons </math> Na<sup>+</sup><sub>(aq)</sub> + Cl<sup>−</sup><sub>(aq)</sub> | |||
| The ] of ionic salts in ] is generally determined by the degree of ] of the ions by water molecules. Such ]es occur by water donating spare ]s on the ] atom to the ion. The behavior of this system is characterised by the ]s of the components and the ], defined as: | |||
| :<ce>\mathit a_{Na+} . \mathit a_{Cl^-} = \mathit{K_{sp}}</ce> | |||
| The ability of an ion to preferentially dissolve (as a result of unequal activities) is classified as the ]. This in turn results in the remaining particle possessing either a net positive/negative surface charge. | |||
| ===Oxides=== | |||
| The dissolution of oxide minerals such as ] occurs by several mechanisms which depend on the composition of the mineral and the chemistry of the solution.<ref name="BrantleyKubicki2008">{{cite book|title=Kinetics of Water-Rock Interaction|last1=Brantley|first1=Susan L.|last2=Kubicki|first2=James D.|last3=White|first3=Art F.|year=2008|pages=151–210|doi=10.1007/978-0-387-73563-4}}</ref> Dissolution rates partially depend on solution ]. Adsorbed ] or ] polarize the mineral surface and weaken cation-oxygen bonds, accelerating dissolution. Silicate minerals containing metal cations undergo '''incongruent dissolution''' as the cations ] out of the mineral faster than the silica lattice degrades. Incongruent dissolution results in a surface layer with different composition than the bulk, called an alteration layer. | |||
| The '''reductive dissolution''' of a ] ] can occur when a ] event in solution reduces a ]. Dissolution occurs when the reduced cation is unstable in the solid material.<ref name="CornellSchwertmann2003-306">{{cite book|title=The Iron Oxides: Structure, Properties, Reactions, Occurrences and Uses, Second Edition|last1=Cornell|first1=R. M.|last2=Schwertmann|first2=U.|year=2003|page=306|doi=10.1002/3527602097}}</ref> In ] such as ], reduction may be caused by ] from organic molecules<ref name="SulzbergerSuter1989">{{cite journal|last1=Sulzberger|first1=Barbara|last2=Suter|first2=Daniel|last3=Siffert|first3=Christophe|last4=Banwart|first4=Steven|last5=Stumm|first5=Werner|title=Dissolution of fe(iii)(hydr)oxides in natural waters; laboratory assessment on the kinetics controlled by surface coordination|journal=Marine Chemistry|volume=28|issue=1-3|year=1989|pages=127–144|issn=0304-4203|doi=10.1016/0304-4203(89)90191-6}}</ref> or bacteria<ref name="Roden2008">{{cite journal|last1=Roden|first1=Eric E.|title=Microbiological Controls on Geochemical Kinetics 1: Fundamentals and Case Study on Microbial Fe(III) Oxide Reduction|year=2008|pages=335–415|doi=10.1007/978-0-387-73563-4_8}}</ref> in ] or soils. Charge carriers responsible for reductive dissolution may also be introduced by ] or by ] poising at negative potentials. Reductive dissolution is integral to natural ] phenomena such as the ].<ref name="CornellSchwertmann2003-323">{{cite book|title=The Iron Oxides: Structure, Properties, Reactions, Occurrences and Uses, Second Edition|last1=Cornell|first1=R. M.|last2=Schwertmann|first2=U.|year=2003|page=323|doi=10.1002/3527602097}}</ref> | |||
| Using ] (<ce>Fe2O3</ce>) as an example, the fundamental formula of reductive dissolution is: | |||
| :<ce>{Fe^3+_(s)} + {e^-} -> {Fe^2+_(aq)}</ce> | |||
| Here, an <ce>{Fe^3+}</ce> cation at the oxide surface captures an ] (<ce>{e^-}</ce>), converting the cation to <ce>{Fe^2+}</ce>. However, <ce>{Fe^2+}</ce> is unstable in the oxide lattice relative to the solution and is subsequently ]d. | |||
| Reductants causing reductive dissolution include natural electron donors such as ] and <ce>{Fe^2+_(aq)}</ce>. Chelating species such as ] accelerate the process by detaching surface-bound <ce>{Fe^2+}</ce>, opening surface sites for further attack by reductants. Reductive dissolution is also promoted by ].<ref name="SulzbergerSuter1989" /> | |||
| Reductive dissolution does not necessarily occur at the site of reductant adsorption, particularly for conductive specimens. Excess electrons injected into a ] particle during a ] event can travel through the particle, causing reductive dissolution elsewhere on the particle.<ref name="YaninaRosso2008">{{cite journal|last1=Yanina|first1=S. V.|last2=Rosso|first2=K. M.|title=Linked Reactivity at Mineral-Water Interfaces Through Bulk Crystal Conduction|journal=Science|volume=320|issue=5873|year=2008|pages=218–222|issn=0036-8075|doi=10.1126/science.1154833|pmid=18323417|bibcode=2008Sci...320..218Y}}</ref> The transport of charge across a hematite particle is driven by differences in the surface potential of different ].<ref name="ChatmanZarzycki2015">{{cite journal|last1=Chatman|first1=S.|last2=Zarzycki|first2=P.|last3=Rosso|first3=K. M.|title=Spontaneous Water Oxidation at Hematite (α-Fe2O3) Crystal Faces|journal=ACS Applied Materials & Interfaces|volume=7|issue=3|year=2015|pages=1550–1559|issn=1944-8244|doi=10.1021/am5067783}}</ref> | |||
| ===Semiconductors=== | |||
| '''Photocorrosion''' is the light-induced degradation and dissolution of semiconductor materials used as electrodes in ]. This can occur when photoexcited charge carriers change the ] of surface atoms or ions, destabilizing the material. Materials with smaller ]s which can absorb larger regions of the ] are more susceptible to photocorrosion.<ref name="LiWu2015">{{cite journal|last1=Li|first1=Jiangtian|last2=Wu|first2=Nianqiang|title=Semiconductor-based photocatalysts and photoelectrochemical cells for solar fuel generation: a review|journal=Catal. Sci. Technol.|volume=5|issue=3|year=2015|pages=1360–1384|issn=2044-4753|doi=10.1039/C4CY00974F}}</ref> In ] using a ] photoelectrode, for example, it is desired that ] (<ce>{h^+}</ce>) generated in <ce>{CdS}</ce> by absorption of photons will oxidize ] species in solution: | |||
| :<ce>2{h^+}+{OH^-}->{1/2O_2}+{H^+}</ce> | |||
| However, in a competing pathway, holes may instead degrade <ce>{CdS}</ce>:<ref name="Ashokkumar1998">{{cite journal|last1=Ashokkumar|first1=M|title=An overview on semiconductor particulate systems for photoproduction of hydrogen|journal=International Journal of Hydrogen Energy|volume=23|issue=6|year=1998|pages=427–438|issn=0360-3199|doi=10.1016/S0360-3199(97)00103-1}}</ref> | |||
| :<ce>2{h^+}+{CdS}->{Cd^2+}+{S}</ce> | |||
| The photocorrosion of some photo-absorbing electrodes can be mitigated by using protective ] coatings.<ref name="HuLewis2015">{{cite journal|last1=Hu|first1=Shu|last2=Lewis|first2=Nathan S.|last3=Ager|first3=Joel W.|last4=Yang|first4=Jinhui|last5=McKone|first5=James R.|last6=Strandwitz|first6=Nicholas C.|title=Thin-Film Materials for the Protection of Semiconducting Photoelectrodes in Solar-Fuel Generators|journal=The Journal of Physical Chemistry C|volume=119|issue=43|year=2015|pages=24201–24228|issn=1932-7447|doi=10.1021/acs.jpcc.5b05976}}</ref> | |||
| === Polar compounds === | |||
| Polar solid compounds can be amorphous or crystalline. Crystalline solids dissolve with breakdown of their crystal lattice, and due to their polarity, or non-polarity, mix with the ].{{dubious|date=June 2015}} | |||
| === Polymers === | |||
| The solubility of ] depends on the chemical bonds present in the backbone chain and their compatibility with those of the solvent.{{dubious|date=June 2015}} The ] is commonly used to evaluate polymer solubility. The closer the value of the parameters, the more likely dissolution will occur.{{vague|date=June 2015}} | |||
| == Rate of dissolution == | |||
| {{Cleanup|section|reason=that the sophistication of the content of this section, esp. the prose following the equation, relative to the rest of the article, makes it suspect with regard to its use of this single paywalled source|date=June 2015}} | |||
| The rate of dissolution quantifies the speed of the dissolution process. It depends on the chemical natures of the solvent and solute,{{vague|date=June 2015}} the temperature (and possibly to a small degree, the pressure), the degree of undersaturation,{{vague|date=June 2015}} the presence of a means of mixing during the dissolution, the interfacial surface area,{{vague|date=June 2015}} and the presence of "inhibitors" (e.g., substances adsorbed on the surface).{{vague|date=June 2015}}{{citation needed|date=June 2015}} | |||
| The rate can be often expressed by the ] or the Nernst and Brunner equation<ref>{{cite journal|first1=Aristides |last1=Dokoumetzidis |first2=Panos |last2=Macheras |date=2006|title=A century of dissolution research: From Noyes and Whitney to the Biopharmaceutics Classification System |journal=Int. J. Pharm. |volume=321|issue=1–2 |pages=1–11 |DOI=10.1016/j.ijpharm.2006.07.011|url=http://www.sciencedirect.com/science/article/pii/S0378517306005813}}</ref> of the form: | |||
| :<math>\frac {dm} {dt} = A \frac {D} {d} (C_\mathrm{s}-C_\mathrm{b})</math> | |||
| where: | |||
| : ''m'' = mass of dissolved material | |||
| : ''t'' = time | |||
| : ''A'' = surface area of the interface between the dissolving substance and the solvent | |||
| : ''D'' = ] | |||
| : ''d'' = thickness of the boundary layer of the solvent at the surface of the dissolving substance | |||
| : ''C''<sub>s</sub> = mass concentration of the substance on the surface | |||
| : ''C''<sub>b</sub> = mass concentration of the substance in the bulk of the solvent | |||
| For dissolution limited by ], ''C''<sub>s</sub> is equal to the solubility of the substance. When the dissolution rate of a pure substance is normalized to the surface area of the solid (which usually changes with time during the dissolution process), then it is expressed in kg/m<sup>2</sup>s and referred to as "intrinsic dissolution rate". The intrinsic dissolution rate is defined by the ]. | |||
| Dissolution rates vary by orders of magnitude between different systems. Typically, very low dissolution rates parallel low solubilities, and substances with high solubilities exhibit high dissolution rates, as suggested by the Noyes-Whitney equation. However, this is not a rule.{{according to whom|date=June 2015}} | |||
| == See also == | |||
| *] | |||
| *] | |||
| *] | |||
| == References == | |||
| {{Reflist}} | |||
| ==Further reading== | |||
| {{Refbegin}} | |||
| *{{cite book|last1=Brady|first1=Patrick V.|first2=William A. |last2=House|chapter=4. Surface-controlled dissolution and growth of minerals|editor-last1=Brady|editor-first1=Patrick V.|title=Physics and chemistry of mineral surfaces|date=1996|publisher=CRC Press|location=Boca Raton, Fla.|isbn=9780849383519|pages=226–298}} | |||
| *{{cite book|editor-last1=Troy|editor-first1=David B.|editor-last2=Beringer|editor-first2=Paul|last1=Kumar|first1=Vijai|last2=Tewari|first2=Divya|chapter=Dissolution|title=Remington: The Science and Practice of Pharmacy|date=2006|publisher=Lippincott Williams & Wilkins|isbn=9780781746731|pages=672–690}} | |||
| *{{cite book|last1=Whitten|first1=Kenneth W.|title=Chemistry|date=2014|publisher=Brooks/Cole Cengage Learning|location=Belmont, CA|isbn=9781133610663|pages=506–514|edition=10th}} | |||
| {{Refend}} | |||
| {{Authority control}} | {{Authority control}} | ||
| ] | |||
Latest revision as of 14:47, 14 July 2021
Redirect to:
- With history: This is a redirect from a page containing substantive page history. This page is kept as a redirect to preserve its former content and attributions. Please do not remove the tag that generates this text (unless the need to recreate content on this page has been demonstrated), nor delete this page.
- This template should not be used for redirects having some edit history but no meaningful content in their previous versions, nor for redirects created as a result of a page merge (use {{R from merge}} instead), nor for redirects from a title that forms a historic part of Misplaced Pages (use {{R with old history}} instead).