Editing Aqueous solution

{{short description|Solution in which the solvent is water}}
{{Redirect|Aqueous|the fluid in the eye|Aqueous humour}}
[[File:Na+H2O.svg|thumb|right|The first [[solvation shell]] of a sodium ion dissolved in water]]

An '''aqueous solution''' is a [[Solution (chemistry)|solution]] in which the [[solvent]] is [[water]]. It is mostly shown in [[chemical equation]]s by appending (aq) to the relevant [[chemical formula]]. For example, a solution of [[table salt]], also known as [[sodium chloride]] (NaCl), in water would be represented as {{chem2|Na+(aq) + Cl−(aq)}}. The word ''aqueous'' (which comes from ''aqua'') means pertaining to, related to, similar to, or [[solvation|dissolved]] in, water.<ref name=":02">{{Cite book |last=Zumdahl |first=Steven |title=Chemistry (4th ed.) |publisher=Houghton Mifflin Company |year=1997 |isbn=9780669417944 |location=Boston, MA |pages=133–145}}</ref><ref>{{Cite journal |last=Sorrenti |first=A. |last2=Illa |first2=O. |last3=Ortuño |first3=R. M. |date=2013-10-07 |title=Amphiphiles in aqueous solution: well beyond a soap bubble |url=https://pubs.rsc.org/en/content/articlelanding/2013/cs/c3cs60151j |journal=Chemical Society Reviews |language=en |volume=42 |issue=21 |pages=8200–8219 |doi=10.1039/C3CS60151J |issn=1460-4744 |pmid=23884241|url-access=subscription }}</ref> As water is an excellent solvent and is also naturally abundant, it is a ubiquitous solvent in [[chemistry]]. Since water is frequently used as the solvent in experiments, the word solution refers to an aqueous solution, unless the solvent is specified.<ref name=":1">{{Cite book |last=Atkins |first=Peter |title=Chemical Principles: The Quest for Insight (3rd ed.) |date=19 March 2004 |publisher=W.H. Freeman and Company |isbn=0-7167-5701-X |location=New York, NY |pages=F61–F64}}</ref><ref>{{Cite web |title=What Is an Aqueous Solution? Chemistry Definition and Example |url=https://www.thoughtco.com/definition-of-aqueous-solution-604370 |access-date=2024-08-24 |website=ThoughtCo |language=en}}</ref>

{{anchor|non-aqueous solution}}A ''non-aqueous solution'' is a solution in which the solvent is a liquid, but is not water.<ref>{{Cite web |title=Solutions |url=http://www.chemistry.wustl.edu/~coursedev/Online%20tutorials/Solutions.htm |url-status=live |archive-url=https://web.archive.org/web/20180425105000/http://www.chemistry.wustl.edu/~coursedev/Online%20tutorials/Solutions.htm |archive-date=25 April 2018 |access-date=13 April 2018 |website=Washington University Chemistry Department |publisher=Washington University}}</ref>

== Characteristics ==
Substances that are ''[[hydrophobic]]'' ('water-fearing') do not dissolve well in water, whereas those that are ''[[hydrophilic]]'' ('water-friendly') do. An example of a hydrophilic substance is sodium chloride. In an aqueous solution the hydrogen ions ({{chem2|H+}}) and hydroxide ions ({{chem2|OH−}}) are in [[Acid–base reaction#Arrhenius theory|Arrhenius]] balance ({{chem2|[H+] [OH−]}} = ''[[Self-ionization of water|K<sub>w</sub>]]'' = 1 x 10<sup>−14</sup> at 298 K).
[[Acid]]s and [[Base (chemistry)|bases]] are aqueous solutions, as part of their [[Acid–base reaction#Arrhenius definition|Arrhenius definitions]].<ref name=":02" /> An example of an Arrhenius acid is [[hydrogen 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.<ref name=":1" />

Aqueous solutions may contain, especially in the alkaline zone or subjected to radiolysis, hydrated atomic hydrogen and [[hydrated electron]]s.{{cn|date=February 2024}}

== Electrolytes ==
Aqueous solutions that conduct [[electric current]] efficiently contain "strong" [[electrolyte]]s, while those that conduct poorly are attributable to  weaker electrolytes. The former substances are completely, or at least substantially,  [[ionization|ionized]] in water; conversely, the weak electrolytes exhibit relatively limited  ionization in water.<ref name=":02" /> The ability of ions to move freely through a solvent is a characteristic of an aqueous strong electrolyte solution; the solutes in a weaker electrolyte solution are present as ions, but only to a small degree.<ref name=":1" />

Non-electrolytes, conversely, are substances that dissolve in water, yet maintain their molecular integrity: they do not dissociate into ions. (Such examples include [[sugar]], [[urea]], [[glycerol]], and [[methylsulfonylmethane]] (MSM).{{cn|date=February  2024}}

== Reactions ==
Reactions in aqueous solutions are usually [[Salt metathesis reaction|metathesis]] reactions. Metathesis reactions are another term for [[double-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.<ref name=":02" />

A common metathesis reaction in aqueous solutions is a [[Precipitation (chemistry)|precipitation]] reaction. This reaction occurs when two aqueous strong electrolyte solutions mix and produce an insoluble solid, also known as a [[Precipitation (chemistry)|precipitate]]. The ability of a substance to dissolve in water is determined by whether the substance can match or exceed the strong [[intermolecular force#Dipole-dipole interactions|attractive forces]] that water molecules generate between themselves. If the substance lacks the ability to dissolve in water, the molecules form a [[Precipitation (chemistry)|precipitate]].<ref name=":1" />

When writing the equations of precipitation reactions, it is essential to determine the precipitate. To determine the precipitate, one must consult a [[Solubility chart|chart of solubility]]. Soluble compounds are aqueous, while insoluble compounds are the precipitate. There may not always be a precipitate. Complete [[ionic equation]]s and net ionic equations are used to show dissociated ions in metathesis reactions. When performing calculations regarding the [[Chemical reaction|reacting]] of one or more aqueous solutions, in general one must know the [[concentration]], or [[molarity]], of the aqueous solutions.{{cn|date=February 2024}}

==See also==
{{Wiktionary}}
* [[Acid–base reaction]]
* [[Acidity function]]
* [[Dissociation (chemistry)]]
* [[Drug permeability]]
* [[Inorganic nonaqueous solvent]]
* [[List of ions in pure water (aqueous chemistry)]]
* [[Metal ions in aqueous solution]]
* [[Properties of water]]
* [[Solubility]]
* [[Solvated electron]]

==References==
{{Reflist}}

{{Chemical solutions}}
{{Authority control}}

[[Category:Chemical properties]]
[[Category:Solutions]]