Anaqueous solutionis asolutionin which thesolventiswater.It is mostly shown inchemical equationsby appending (aq) to the relevantchemical formula.For example, a solution oftable salt,also known assodium chloride(NaCl), in water would be represented asNa+(aq) + Cl−(aq).The wordaqueous(which comes fromaqua) means pertaining to, related to, similar to, ordissolvedin, water.[1][2]As water is an excellent solvent and is also naturally abundant, it is a ubiquitous solvent inchemistry.Since water is frequently used as the solvent in experiments, the word solution refers to an aqueous solution, unless the solvent is specified.[3][4]
Anon-aqueous solutionis a solution in which the solvent is a liquid, but is not water.[5]
Characteristics
editSubstances that arehydrophobic('water-fearing') do not dissolve well in water, whereas those that arehydrophilic('water-friendly') do. An example of a hydrophilic substance is sodium chloride. In an aqueous solution the hydrogen ions (H+) and hydroxide ions (OH−) are inArrheniusbalance ([H+] [OH−]=Kw= 1 x 10−14at 298 K). Acidsandbasesare aqueous solutions, as part of theirArrhenius definitions.[1]An example of an Arrhenius acid ishydrogen chloride(HCl) because of its dissociation of the hydrogen ion when dissolved in water.Sodium hydroxide(NaOH) is an Arrhenius base because it dissociates the hydroxide ion when it is dissolved in water.[3]
Aqueous solutions may contain, especially in the alkaline zone or subjected to radiolysis, hydrated atomic hydrogen andhydrated electrons.[citation needed]
Electrolytes
editAqueous solutions that conductelectric currentefficiently contain strongelectrolytes,while ones that conduct poorly are considered to have weak electrolytes. Those strong electrolytes are substances that are completelyionizedin water, whereas the weak electrolytes exhibit only a small degree of ionization in water.[1]The ability for ions to move freely through the solvent is a characteristic of an aqueous strong electrolyte solution. The solutes in a weak electrolyte solution are present as ions, but only in a small amount.[3]
Nonelectrolytes are substances that dissolve in water yet maintain their molecular integrity (do not dissociate into ions). Examples includesugar,urea,glycerol,andmethylsulfonylmethane(MSM).[citation needed]
Reactions
editReactions in aqueous solutions are usuallymetathesisreactions. Metathesis reactions are another term fordouble-displacement;that is, when a cation displaces to form an ionic bond with the other anion. The cation bonded with the latter anion will dissociate and bond with the other anion.[1]
A common metathesis reaction in aqueous solutions is aprecipitationreaction. This reaction occurs when two aqueous strong electrolyte solutions mix and produce an insoluble solid, also known as aprecipitate.The ability of a substance to dissolve in water is determined by whether the substance can match or exceed the strongattractive forcesthat water molecules generate between themselves. If the substance lacks the ability to dissolve in water, the molecules form aprecipitate.[3]
When writing the equations of precipitation reactions, it is essential to determine the precipitate. To determine the precipitate, one must consult achart of solubility.Soluble compounds are aqueous, while insoluble compounds are the precipitate. There may not always be a precipitate. Completeionic equationsand net ionic equations are used to show dissociated ions in metathesis reactions. When performing calculations regarding thereactingof one or more aqueous solutions, in general one must know theconcentration,ormolarity,of the aqueous solutions.[citation needed]
See also
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References
edit- ^abcdZumdahl, Steven (1997).Chemistry (4th ed.).Boston, MA: Houghton Mifflin Company. pp. 133–145.ISBN9780669417944.
- ^Sorrenti, A.; Illa, O.; Ortuño, R. M. (2013-10-07)."Amphiphiles in aqueous solution: well beyond a soap bubble".Chemical Society Reviews.42(21): 8200–8219.doi:10.1039/C3CS60151J.ISSN1460-4744.PMID23884241.
- ^abcdAtkins, Peter (19 March 2004).Chemical Principles: The Quest for Insight (3rd ed.).New York, NY: W.H. Freeman and Company. pp. F61–F64.ISBN0-7167-5701-X.
- ^"What Is an Aqueous Solution? Chemistry Definition and Example".ThoughtCo.Retrieved2024-08-24.
- ^"Solutions".Washington University Chemistry Department.Washington University.Archivedfrom the original on 25 April 2018.Retrieved13 April2018.