Acidity function

An acidity function is a measure of the acidity of a medium or solvent system,^[1]^[2] usually expressed in terms of its ability to donate protons to (or accept protons from) a solute (Brønsted acidity). In Computer science, ACID ( Atomicity Consistency Isolation Durability) is a set of properties that guarantee that Database transactions are In Chemistry, a base is most commonly thought of as an aqueous substance that can accept Protons This refers to the Brønsted-Lowry theory of acids and Acid-base extraction is a procedure using sequential Liquid-liquid extractions to purify Acids and bases from mixtures based on their chemical properties Acid-base homeostasis is the part of Human homeostasis concerning the proper balance between Acids and bases, in other words the PH. For an individual weak acid or weak base component see Buffering agent. pH is the measure of the acidity or alkalinity of a Solution. The proton affinity, E pa of a Anion or of a neutral Atom or Molecule is a measure of its gas-phase basicity. The self-ionization of water (also autoionization of water, and autodissociation of water) is the chemical reaction in which two water molecules react to produce a In Computer science, ACID ( Atomicity Consistency Isolation Durability) is a set of properties that guarantee that Database transactions are A mineral acid is an Acid derived by Chemical reaction from inorganic Minerals as opposed to Organic acids These have Hydrogen An organic acid is an Organic compound with Acidic properties A Strong acid is an Acid that Ionizes completely in an Aqueous solution (not in the case of Sulfuric acid as it is diprotic A superacid is an Acid with an Acidity greater than that of 100% Sulfuric acid, which has a Hammett acidity function ( H 0 A weak acid is an Acid that does not completely donate all of its hydrogens when dissolved in water In Chemistry, a base is most commonly thought of as an aqueous substance that can accept Protons This refers to the Brønsted-Lowry theory of acids and An organic base is an Organic compound which acts as a base. Organic bases are usually but not always proton acceptors In Chemistry, a base is most commonly thought of as an aqueous substance that can accept Protons This refers to the Brønsted-Lowry theory of acids and In Chemistry, a superbase is an extremely strong base. There is no commonly accepted definition for what qualifies as a superbase but most chemists would accept As the name suggests a non-nucleophilic base is an organic base that is a very Strong base but at the same time a poor Nucleophile. In chemistry a weak base is a Chemical base that does not Ionize fully in an Aqueous solution. In Computer science, ACID ( Atomicity Consistency Isolation Durability) is a set of properties that guarantee that Database transactions are In Chemistry, a solution is a Homogeneous Mixture composed of two or more substances In Computer science, ACID ( Atomicity Consistency Isolation Durability) is a set of properties that guarantee that Database transactions are The pH scale is by far the most commonly used acidity function, and is ideal for dilute aqueous solutions. pH is the measure of the acidity or alkalinity of a Solution. Other acidity functions have been proposed for different environments, most notably the Hammett acidity function, H₀,^[3] for superacid media and its modified version H₋ for superbasic media. The Hammett acidity function is a measure of acidity that is used for very concentrated solutions of strong acids including Superacids. A superacid is an Acid with an Acidity greater than that of 100% Sulfuric acid, which has a Hammett acidity function ( H 0 In Chemistry, a superbase is an extremely strong base. There is no commonly accepted definition for what qualifies as a superbase but most chemists would accept The term acidity function is also used for measurements made on basic systems, and the term basicity function is uncommon.

Hammett-type acidity functions are defined in terms of a buffered medium:

$H_0 = {\rm p}K_{\rm a} + \log {{c_{\rm B}}\over{c_{\rm BH^+}}}$

where pK_a is the dissociation constant of BH⁺. For an individual weak acid or weak base component see Buffering agent. They were originally measured by using nitroanilines as acid-base indicators and by measuring the concentrations of the protonated and unprotonated forms with UV-visible spectroscopy. A pH indicator is a halochromic chemical compound that is added in small amounts to a Solution so that the PH ( Acidity or Ultraviolet-visible spectroscopy or ultraviolet-visible spectrophotometry ( UV/ VIS) involves the Spectroscopy of Photons in the UV-visible ^[3] Other spectroscopic methods, such as NMR, may also be used. Nuclear magnetic resonance spectroscopy, most commonly known as NMR spectroscopy, is the name given to a technique which exploits the magnetic properties of certain nuclei ^[2]^[4] The function H₋ is defined similarly:

$H_- = {\rm p}K_{\rm a} + \log {{c_{\rm B^-}}\over{c_{\rm BH}}}$

Comparison of acidity functions with aqueous acidity

In dilute aqueous solution, H₀ and H₋ are equivalent to pH values determined by the buffer equation. However, an H₀ value of −21 (a 25% solution of SbF₅ in HSO₃F)^[5] does not imply a hydrogen ion concentration of 10²¹ mol/dm³: such a "solution" would have a density more than a hundred times greater than than a neutron star. Antimony pentafluoride is the Chemical compound with the formula Sb[[Fluorine F]]5 Fluorosulfuric acid is FSO3H it is one of the strongest acids commercially available A neutron star is a type of remnant that can result from the Gravitational collapse of a massive Star during a Type II, Type Ib or Type Rather, H₀ = −21 implies that the reactivity of the solvated hydrogen ions is 10²¹ times greater than the reactivity of the hydrated hydrogen ions in an aqueous solution of pH 0. The actual reactive species are different in the two cases, but both can be considered to be sources of H⁺, i. e. Brønsted acids. In Computer science, ACID ( Atomicity Consistency Isolation Durability) is a set of properties that guarantee that Database transactions are The hydrogen ion H⁺ never exists on its own in a condensed phase, it is always solvated to a certain extent. Solvation, commonly called dissolution, is the process of attraction and association of Molecules of a Solvent with molecules or Ions of a The high negative value of H₀ in SbF₅/HSO₃F mixtures indicates that the solvation of the hydrogen ion is much weaker in this solvent system than in water. Other way of expressing the same phenomenon is to say that SbF₅·FSO₃H is a much stronger proton donor than [H(OH₂)₂]⁺.

References

^ IUPAC Commission on Physical Organic Chemistry (1994). The International Union of Pure and Applied Chemistry ( IUPAC) (aɪjuːpæk or ay-yoo-pec) is an international Non-governmental organization "Glossary of Terms used in Physical Organic Chemistry." Pure Appl. Chem. 66:1077–1184. Pure and Applied Chemistry (abb Pure Appl Chem) is the official journal for the International Union of Pure and Applied Chemistry. "Acidity function." Compendium of Chemical Terminology. Compendium of Chemical Terminology (ISBN 0-86542-684-8 is a book published by IUPAC containing internationally accepted definitions for terms in Chemistry.
^ ^a ^b Rochester, C. H. (1970). Acidity Functions. New York: Academic Press.
^ ^a ^b Hammett, L. P. (1940). Louis Plack Hammett (April 7 1894 - February 9 1987 was an American Physical chemist. Physical Organic Chemistry. New York: McGraw-Hill.
^ Cox, R. A. ; Yates, K. (1983). Can. J. Chem. 61:2245. The Canadian Journal of Chemistry (print- ISSN 0008-4042 CODEN CJCHAG is a Peer-reviewed Scientific journal published by the
^ Jolly, William L. (1991). Modern Inorganic Chemistry (2nd Edn. ). New York: McGraw-Hill. ISBN 0-07-112651-1. p. 234.

Dictionary

-noun

(chemistry) The relationship between the acidity of a solution and the concentration of its solute

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