Baza (hemija) – razlika između verzija
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[[Datoteka:AcidBase%E2%80%93pfe.png|mini|250px|Dijagram promjene [[Gibsova slobodna energija|Gibsove slobodne energije]] za disocijaciju nekih [[kiseline|kiselina]] i baza]]
'''Baze''' ili '''lužine''' ([[grčki jezik|grč.]] ''βάση'', ''basé – osnova, fundament'') je jedna od osnovnih kategorija [[hemijsko jedinjenje|hemijskih jedinjenja]]. Baze su u užem smislu svi jedinjenja, koja u vodenim rastvorima mogu graditi hidroksidne [[jon]]e (OH<sup>−</sup>), te tako povisiti [[pH vrednost|pH]] vrednost rastvora. Hidroksilni joni su hemijska jedinjenja koja iz [[kiseline|kiselina]] mogu preuzeti [[proton]]e dajući molekule [[voda|vode]]. Stoga je baza na neki način suprotnost kiselinama te se s njima [[neutralizacija (hemija)|neutralizira]]. U širem smislu, razni bazno-kiselinski koncepti opisuju daleko širu paletu hemijskih reakcija, koji prelaze okvire osobina hidroksidnih jona u vodi. Od posebnog značaja su koncepti po Luisu (Luisove baze i Luisove kiseline),<ref>{{cite web|url=http://goldbook.iupac.org/B00601.html|title=IUPAC Gold Book — base|accessdate=2013-04-18|archiveurl=http://www.webcitation.org/6GGygQCl7|archivedate=2013-04-30}}</ref> te prema Pearsonu, koji navodi podelu na jake i slabe kiseline i baze.<ref>{{cite book |author = Рудзитис Г. Е., Фельдман Ф. Г. |title = Химия. Неорганическая химия. Органическая химия. 9 класс |issue = 13-е изд |location = М. |publisher = Просвещение |year = 2009 |isbn=978-5-09-021-625-8}}</ref>
Većina baza su supstance koje proizvode [[hidroksid]]ne jone (OH<sup>−</sup>) u vodenim rastvorima, i stoga se klasifikuju kao [[Arenijusova baza|Arenijusove base]].<ref name="ХЭ">{{cite book |title=Химическая энциклопедия |editor = Под ред. И. Л. Кнунянца |location = М |publisher = Большая Российская энциклопедия |year = 1992 |volume = 2 |pages = 393—395|isbn=5-85270-039-8 |ref=Химическая энциклопедия}}</ref> For a substance to be classified as an Arrhenius base, it must produce hydroxide ions in an aqueous solution. In order to do so, Arrhenius believed the base must contain hydroxide in the formula. This makes the Arrhenius model limited, as it cannot explain the basic properties of aqueous solutions of [[ammonia]] (NH<sub>3</sub>) or its organic derivatives ([[amine]]s).<ref name="Chemistry 9E">''Chemistry'', 9th Edition. Kenneth W. Whitten, Larry Peck, Raymond E. Davis, Lisa Lockwood, George G. Stanley. (2009) ISBN 0-495-39163-8. Page 363</ref> There are also bases that do not contain a hydroxide ion but nevertheless react with water, resulting in an increase in the concentration of the hydroxide ion.<ref name="Chemical Principles">{{cite book|last1=Zumdahl|first1=Steven|last2=DeCoste|first2=Donald|title=Chemical Principles|date=2013|publisher=Mary Finch|pages=257|edition=7th|accessdate=11 February 2015}}</ref> An example of this is the reaction between ammonia and water to produce ammonium and hydroxide.<ref name="Chemical Principles"/> In this reaction ammonia is the base because it accepts a proton from the water molecule.<ref name="Chemical Principles"/> Ammonia and other bases similar to it usually have the ability to form a bond with a proton due to the unshared pair of unshared electrons that they possess<ref name="Chemical Principles"/> In the more general [[Brønsted–Lowry acid–base theory]], a base is a substance that can accept [[hydron (chemistry)|hydrogen ion]]s (H<sup>+</sup>)—otherwise known as [[proton]]s. In the [[Lewis acids and bases|Lewis model]], a base is an [[electron pair]] donor.<ref>''Chemistry''. Page 349</ref>▼
▲For a substance to be classified as an Arrhenius base, it must produce hydroxide ions in an aqueous solution. In order to do so, Arrhenius believed the base must contain hydroxide in the formula. This makes the Arrhenius model limited, as it cannot explain the basic properties of aqueous solutions of [[ammonia]] (NH<sub>3</sub>) or its organic derivatives ([[amine]]s).<ref name="Chemistry 9E">''Chemistry'', 9th Edition. Kenneth W. Whitten, Larry Peck, Raymond E. Davis, Lisa Lockwood, George G. Stanley. (2009) ISBN 0-495-39163-8. Page 363</ref> There are also bases that do not contain a hydroxide ion but nevertheless react with water, resulting in an increase in the concentration of the hydroxide ion.<ref name="Chemical Principles">{{cite book|last1=Zumdahl|first1=Steven|last2=DeCoste|first2=Donald|title=Chemical Principles|date=2013|publisher=Mary Finch|pages=257|edition=7th|accessdate=11 February 2015}}</ref> An example of this is the reaction between ammonia and water to produce ammonium and hydroxide.<ref name="Chemical Principles"/> In this reaction ammonia is the base because it accepts a proton from the water molecule.<ref name="Chemical Principles"/> Ammonia and other bases similar to it usually have the ability to form a bond with a proton due to the unshared pair of unshared electrons that they possess<ref name="Chemical Principles"/> In the more general [[Brønsted–Lowry acid–base theory]], a base is a substance that can accept [[hydron (chemistry)|hydrogen ion]]s (H<sup>+</sup>)—otherwise known as [[proton]]s. In the [[Lewis acids and bases|Lewis model]], a base is an [[electron pair]] donor.<ref>''Chemistry''. Page 349</ref>
In water, by altering the [[self-ionization of water|autoionization]] [[Chemical equilibrium|equilibrium]], bases yield solutions in which the hydrogen ion [[Activity (chemistry)|activity]] is lower than it is in pure water, i.e., the water has a [[pH]] higher than 7.0 at standard conditions. A soluble base is called an '''[[alkali]]''' if it contains and releases OH<sup>−</sup> ions [[Stoichiometry|quantitatively]]. However, it is important to realize that basicity is not the same as [[alkalinity]]. Metal [[oxide]]s, hydroxides, and especially [[alkoxide]]s are basic, and counteranions of [[acid strength|weak acid]]s are weak bases.
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