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'''Alkali''' (dari {{Lang-ar|القلي, القالي}}, "abu dari lumut asin") dalam [[kimia]] adalah suatu [[garam]] [[ion]]ik [[basa]] dari suatu [[unsur kimia]] [[alkali logam]] atau [[alkali tanah]]. Ada yang mendefinisikan suatu alkali sebagai suatu zat [[basa]] yang larut dalam [[air]]. Larutan alkali mempunyai [[pH]] lebih dari 7,0.<!--The [[adjective]] '''alkaline''' is commonly, and '''alkalescent''' less often, used in [[English language|English]] as a [[synonym]] for basic, especially for [[soluble]] bases. This broad use of the term is likely to have come about because alkalis were the first bases known to obey the [[acid-base reaction theories|Arrhenius]] definition of a base, and they are still among the most common bases.
==Etymology==
The word "alkali" is derived from Arabic ''al qalīy'' (or ''alkali''),<ref>{{cite book|title=[[Chambers's encyclopaedia]]: a dictionary of universal knowledge, Volume 1|publisher=J.B. Lippincott & Co|year=1888|page=148}}</ref> meaning ''the calcined ashes'' (see [[calcination]]), referring to the original source of alkaline substances. A water-extract of burned plant ashes, called [[potash]] and composed mostly of potassium carbonate, was mildly basic. After heating this substance with [[calcium hydroxide]] (''slaked lime''), a far more strongly basic substance known as ''caustic potash'' ([[potassium hydroxide]]) was produced. Caustic potash was traditionally used in conjunction with animal fats to produce soft [[soap]]s, one of the caustic processes that rendered soaps from fats in the process of [[saponification]], one known since antiquity. Plant potash lent the name to the element [[potassium]], which was first derived from caustic potash, and also gave potassium its chemical symbol '''K''' (from the German name Kalium), which ultimately derived from al'''k'''ali.
==Common properties==
Alkalis are all Arrhenius bases, ones which form hydroxide ions (OH<sup>-</sup>) when dissolved in water. Common properties of alkaline aqueous [[solution]]s include:
* Moderately concentrated solutions (over 10<sup>−3</sup> M) have a pH of 7.1 or greater. This means that they will turn [[phenolphthalein]] from colorless to pink.
* Concentrated solutions are [[Caustic (substance)|caustic]] (causing chemical burns).
* Alkaline solutions are slippery or soapy to the touch, due to the [[saponification]] of the fatty substances on the surface of the skin.
* Alkalis are normally [[solubility|water soluble]], although some like [[barium carbonate]] are only soluble when reacting with an acidic aqueous solution.
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== Perbedaan antara alkali dan basa ==
Istilah "basa" dan "alkali" sering digunakan bergantian, terutama di luar konteks [[kimia]] dan teknik kimia.
<!--
There are various definitions for the concept of an alkali. Alkalis are sometimes defined as a subset of the bases. However, two subsets are commonly chosen.
* A basic salt of an alkali metal or alkaline earth metal<ref>[http://dictionary.reference.com/search?q=alkali Alkali | Define Alkali at Dictionary.com]. Dictionary.reference.com. Retrieved on 2012-04-18.</ref> (This includes Mg(OH)<sub>2</sub> but excludes NH<sub>3</sub>.)
* Any base that is soluble in water and forms hydroxide ions<ref>[http://www.tiscali.co.uk/reference/encyclopaedia/hutchinson/m0029936.html alkali]. Tiscali.co.uk. Retrieved on 2012-04-18.</ref><ref>[http://www.thefreedictionary.com/alkali alkali–definition of alkali by the Free Online Dictionary, Thesaurus and Encyclopedia]. Thefreedictionary.com. Retrieved on 2012-04-18.</ref><ref>[http://web.archive.org/web/20061124183909/http://www.wahyan.edu.hk/paulsir/handout/form4/4-05_Characteriscs_of_alkali.pdf Characteristics of Alkali]. (from L.H.M. Chung ''Integrated Chemistry Today'' pp. 363–365)</ref> or the solution of a base in water.<ref>[http://www.krysstal.com/acidbase.html Acids, Bases and Salts]. KryssTal. Retrieved on 2012-04-18.</ref> (This excludes Mg(OH)<sub>2</sub> but includes NH<sub>3</sub>.)
The second subset of bases is also called an "Arrhenius base".
==Alkali salts==
Alkali salts are soluble hydroxides of [[alkali metals]] and [[alkaline earth metals]], of which common examples are:
* [[Sodium hydroxide]] - often called "caustic soda"
* [[Potassium hydroxide]] - commonly called "caustic potash"
* [[wikt:lye|Lye]] - generic term for either of the previous two or even for a mixture
* [[Calcium hydroxide]] - saturated solution known as "[[limewater]]"
* [[Magnesium hydroxide]] - an atypical alkali since it has low solubility in water (although the dissolved portion is considered a strong base due to complete dissociation of its ions)
==Tanah alkali ==
Soils with pH values higher than 7.3 are usually defined as being alkaline. These soils can occur naturally, due to the presence of alkali salts. Although some plants do prefer slightly basic soil (including vegetables like [[cabbage]] and fodder like [[buffalograss]]), most plants prefer a mildly acidic soil (with pHs between 6.0 and 6.8), and [[alkaline soil]]s can cause problems.<ref>{{cite book|title=[[Chambers's encyclopaedia]]: a dictionary of universal knowledge, Volume 1|publisher=J.B. Lippincott & Co|year=1888|page=148}}</ref>
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== Danau alkali ==
Dalam ''[[danau alkali]]'' (atau ''danau soda''), penguapan terkonsentrasi pada garam-garam karbonat alamiah, menghasilkan danau alkali yang sering kali juga asin.
Contoh danau alkali:
* [[Alkali Lake (Oregon)|Alkali Lake]], [[Lake County, Oregon]]
* [[Baldwin Lake (San Bernardino County, California)|Baldwin Lake]], [[San Bernardino County, California]]
* [[Mono lake]], near [[Owens Valley]] in [[California]]
* [[Redberry Lake, Saskatchewan]] <!-- Not Blueberry lake, ref see http://www.pnr-rpn.ec.gc.ca/nature/whp/sanctuaries/dc01s12.en.html -->
* [[Summer Lake (Oregon)|Summer Lake]], [[Lake County, Oregon]]
* [[Tramping Lake, Saskatchewan]]
* [[Lake Magadi]] di [[Kenya]]
* [[Lake Turkana]] in [[Kenya]] (danau alkali terbesar di dunia)
* There are also alkali lakes in the outback of [[Australia]].
== Lihat pula ==
* [[Alkali logam]]
* [[Alkali tanah]]
== Referensi ==
{{Reflist|30em}}
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[[Kategori:Kimia]]
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