Réaksi asam-basa

Réaksi asam-basa hartina réaksi kimia antara asam jeung basa.

Téori umum asam-basa

Definisi Lavoisier

Definisi ilmiah munggaran diajukeun ku kimiawan Prancis, Antoine Lavoisier.

ku sabab pangaweruh Lavoisier ngeunaan asam kuat mah utamana ngeunaan asam-oksi, nu condong ngandung atom puseur nu status oksidasina luhung dikuriling oksigén, kayaning HNO₃ jeung H₂SO₄, jeung ku sabab anjeunna mah teu pati awas kana komposisi asam hidrohalat nu sabenerna (HCl, HBr, jeung HI), anjeunna ngahartikeun asam dina jihat kandungan oksigénna, which in fact he named from Greek words méaning "acid-former". When the elements chlorine, bromine, and iodine were identified and the absence of oxygen in the hydrohalic acids was established by Sir Humphry Davy in 1810, this definition had to be rejected.

Definisi Arrhenius

Svante Arrhenius menyediakan definisi modérn munggaran ngeunaan asam jeung basa ditahun1884. Dina cai, lumangsung prosés disosiasi:

H₂O → H⁺ + OH^-

Sanyawa nu ngabalukarkeun ngaronjatna kadar H⁺ sarta nurunkeun kadar OH^- disebut asam, mun sabalikna, disebut basa.

Asam Arrhenius, mun ngalaman disosiasi na cai, bakal ngahasilkeun ion hidrogén nu muatanana positif jeung ion lawanna nu négatif.

Basa Arrhenius, mun ngalaman disosiasi na cai, bakal ngahasilkeun ion hidroksida nu muatanana négatif jeung ion lawanna.

Ion positif ti hiji basa bisa ngahasilkeun uyah jeung ion négatif ti hiji asam. Pikeun conto, dua mol basa natrium hidroksida (NaOH) bisa ngagabung jeung sa-mol asam sulfat (H₂SO₄) ngahasilkeun dua mol cai jeung sa-mol natrium sulfat.

2NaOH + H₂SO₄ → 2H₂O + Na₂SO₄

Definisi proton (Brønsted-Lowry)

Definisi Brønsted-Lowry, dirumuskeun sacara mandiri ku masing-masing Johannes Nicolaus Brønsted jeung Martin Lowry taun 1923, revolves around an acid's ability to donate protons (H⁺) to another compound, called a base, in a chemical réaction.

Basa hartina akséptor proton. Dina réaksi asam-basa Brønsted-Lowry, aya kompetisi antara dua basa marebutkeun hiji proton, antukna mun X jeung Y mangrupa dua spésiés, bakal lumangsung kasatimbangan

HX + Y^- ↔ HY + X^-

Boh HX jeung HY duanana mangrupa asam Brønsted-Lowry; boh X^- jeung Y^- duanana mangrupa basa Brønsted-Lowry. Mun réaksina leuwih loba lumangsung ka kénca, HY mangrupa asam nu leuwih kuat, sedengkeun X^- basa nu leuwih kuat; mun réaksina géséh ka katuhu, mangka HX asam leuwih kuat, sedengkeun Y^- basa leuwih kuat.

It may be more intuitive to define the stronger of two acids as the one which réacts more completely with a common base. The following shows that this definition gives the same result. Compare the réactions of the two acids HX and HY with the same base Z^- (in a mixture containing all these species):

HX + Z^- ↔ HZ + X^-

HY + Z^- ↔ HZ + Y^-

If these réactions have equilibrium constants K_X and K_Y respectively, then:

[X^-][HZ] / [HX][Z^-]=K_X

[Y^-][HZ] / [HY][Z^-]=K_Y

and hence (dividing):

[X^-][HY] / [HX][Y^-] = K_X / K_Y

Given that this last quantity is the equilibrium constant for the above réaction, the réaction will tend to the right if K_X / K_Y > 1, in other words if HX is a stronger acid than HY under this definition, and vice versa.

Acids and bases in the Brønsted-Lowry system occur in conjugate pairs; in the réaction

HX → H⁺ + X^-

HX is called the conjugate acid of the base X^-, and X^- is called the conjugate base of the acid HX.

Some compounds, like water, can act either as an acid or a base, and are called amphoteric compounds.

Stronger acids typically oxidize metals, forming salts and reléasing hydrogen.

See pH for a méasure of proton concentration frequently used for méasuring acidity and alkalinity using this definition. For a list of conjugate acid-base pairs, see conjugate acid.

Definisi pangleyur-sistim

This definition is based on a generalization of the éarlier Arrhenius definition. If we consider a solvent which can be dissociated into a positive species X and a negative species Y:

XY ↔ X⁺ + Y^-

or

2XY ↔ X₂Y⁺ + Y^-

or

2XY ↔ X⁺ + XY₂^-

a compound causing an incréase in X⁺ (or X₂Y⁺) and a decréase in Y^- (or XY₂^-) is an acid and one causing the reverse is a base. For example in liquid sulfur dioxide (SO₂), thionyl compounds (formally supplying SO²⁺) behave as acids, and sulfites (supplying SO₃^2-) behave as bases.

In this more general sense, aprotic compounds (those which do not donate protons), can still réact with bases, and the terms "acid" and "base" can still be used for réactions in aprotic or non-aquéous environments.

Definisi éléktronik (Lewis)

The more general definition offered by Lewis in 1923 (the same yéar as the Brønsted-Lowry definition) describes the réactivity of an acid in terms of its ability to accept a pair of electrons from a base, defined as an electron-pair donor. In general, an acid réacts with a base by forming a new covalent bond utilizing an empty orbital of the acid to share the extra electron pair of the base. That is an acid-base réaction is the combination of HOMO from base and LUMO from acid to form a stable bonding molecular orbital.

The Lewis definition is one of the most broad definitions and is necessary for an understanding of acid-base réaction, although the Brønsted-Lowry definition is sufficient and more practical for most cases in everyday use.

Téori asam-basa lianna

Definisi Usanovich

The most general definition is that of the Russian chemist Usanovich, and can basically be summarized as defining an acid as anything that accepts negative species or donates positive ones, and a base as the reverse. This tends to overlap the concept of redox (oxidation-reduction), and so is not highly favored by chemists. This is because redox réactions focus more on physical electron transfer processes, rather than bond making/bond bréaking processes, although the distinction between these two processes is somewhat ambiguous.

Sumber rujukan

• Acid-base reaction theories, ti Wikipédia basa Inggris, disalin ping 1 Agustus 2005.

Tempo ogé

• Konsép HSAB
• Konfigurasi éléktron