Search results
Results from the WOW.Com Content Network
Acid strength is the tendency of an acid, symbolised by the chemical formula, to dissociate into a proton, +, and an anion, .The dissociation or ionization of a strong acid in solution is effectively complete, except in its most concentrated solutions.
Lewis acids and bases are commonly classified according to their hardness or softness. In this context hard implies small and nonpolarizable and soft indicates larger atoms that are more polarizable. typical hard acids: H +, alkali/alkaline earth metal cations, boranes, Zn 2+ typical soft acids: Ag +, Mo(0), Ni(0), Pt 2+
The acid, HA, is a proton donor which can lose a proton to become its conjugate base, A −. The base, B, is a proton acceptor which can become its conjugate acid, HB +. Most acid–base reactions are fast, so the substances in the reaction are usually in dynamic equilibrium with each other. [8]
Nitric acid, with a pK value of around −1.7, behaves as a strong acid in aqueous solutions with a pH greater than 1. [23] At lower pH values it behaves as a weak acid. pK a values for strong acids have been estimated by theoretical means. [24] For example, the pK a value of aqueous HCl has been estimated as −9.3.
On the other hand, if a chemical is a weak acid its conjugate base will not necessarily be strong. Consider that ethanoate, the conjugate base of ethanoic acid, has a base splitting constant (Kb) of about 5.6 × 10 −10, making it a weak base. In order for a species to have a strong conjugate base it has to be a very weak acid, like water.
Fluoroantimonic acid is a mixture of hydrogen fluoride and antimony pentafluoride, containing various cations and anions (the simplest being H 2 F + and Sb F − 6).This mixture is a superacid that, in terms of corrosiveness, is trillions of times stronger than pure sulfuric acid when measured by its Hammett acidity function.
The higher the proton affinity, the stronger the base and the weaker the conjugate acid in the gas phase.The (reportedly) strongest known base is the ortho-diethynylbenzene dianion (E pa = 1843 kJ/mol), [3] followed by the methanide anion (E pa = 1743 kJ/mol) and the hydride ion (E pa = 1675 kJ/mol), [4] making methane the weakest proton acid [5] in the gas phase, followed by dihydrogen.
Hexafluoroantimonate is the conjugate base of the superacid fluoroantimonic acid HF·SbF 6. As fluoroantimonic acid is one of the strongest known acids (only weaker than the helium hydride ion and potentially some carborane acids), hexafluoroantimonate is one of the weakest known bases. Higher fluoroantimonates are believed to be even less basic