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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.
Any acid with a value which is less than about -2 behaves as a strong acid. This results from the very high buffer capacity of solutions with a pH value of 1 or less and is known as the leveling effect. [3] The following are strong acids in aqueous and dimethyl sulfoxide solution.
A strong superacid of this kind is fluoroantimonic acid. Another group of superacids, the carborane acid group, contains some of the strongest known acids. Finally, when treated with anhydrous acid, zeolites (microporous aluminosilicate minerals) will contain superacidic sites within their pores.
Sulfonic acids are strong acids. They are commonly cited as being around a million times stronger than the corresponding carboxylic acid. For example, p-Toluenesulfonic acid and methanesulfonic acid have pK a values of −2.8 and −1.9, respectively, while those of benzoic acid and acetic acid are 4.20 and 4.76, respectively.
As indicated by its acid dissociation constant, sulfuric acid is a strong acid: H 2 SO 4 → H 3 O + + HSO − 4 K a1 = 1000 (pK a1 = −3) The product of this ionization is HSO − 4, the bisulfate anion. Bisulfate is a far weaker acid: HSO − 4 + H 2 O → H 3 O + + SO 2− 4 K a2 = 0.01 (pK a2 = 2) [20] The product of this second ...
Although hydrofluoric acid is regarded as a weak acid, it is very corrosive, even attacking glass when hydrated. [20] Dilute solutions are weakly acidic with an acid ionization constant K a = 6.6 × 10 −4 (or pK a = 3.18), [10] in contrast to corresponding solutions of the other hydrogen halides, which are strong acids (pK a < 0).
Carborane acids H(CXB 11 Y 5 Z 6) (X, Y, Z = H, Alk, F, Cl, Br, CF 3) are a class of superacids, [1] some of which are estimated to be at least one million times stronger than 100% pure sulfuric acid in terms of their Hammett acidity function values (H 0 ≤ –18) and possess computed pK a values well below –20, establishing them as some of the strongest known Brønsted acids.
Sulfamic acid is a moderately strong acid, K a = 0.101 (pK a = 0.995). Because the solid is not hygroscopic, it is used as a standard in acidimetry (quantitative assays of acid content). H 3 NSO 3 + NaOH → NaH 2 NSO 3 + H 2 O. Double deprotonation can be effected in liquid ammonia to give the anion HNSO 2− 3. [6] H 3 NSO 3 + 2 NH 3 → HNSO ...