Which is the strongest acid?

The strongest superacid known to date is fluoroantimonic acid, a mixture of hydrofluoric acid (HF) and antimony pentafluoride (SbF5). Among them, hydrofluoric acid provides protons (H+) and the conjugate base fluoride ion (F−). The fluoride ion forms an antimony hexafluoride anion (SbF6−) with an octahedrally stable structure through strong coordination bonds with the fluorophilic antimony pentafluoride; this anion is a very weak nucleophile and a very weak base. As a result, the protons become “free protons,” which makes the integrated system highly acidic. The acidity of fluoroantimonic acid is usually 2×1019 times that of pure sulfuric acid.

The strongest acid is: magic acid. Magic acid is a solution composed of two or more fluorine-containing compounds. For example, when hydrofluoric acid and antimony pentafluoride are mixed in a 1:0.3 molar ratio, its acidity is 100 million times that of concentrated sulfuric acid ； When mixed in a 1:1 ratio, its acidity is 1 billion times that of concentrated sulfuric acid. It can dissolve high-grade alkane candles that are insoluble in aqua regia. The essence of acid-base neutralization reactions is a proton transfer reaction. Superacids are acids whose acidity is 10^6 to 10^10 times stronger than that of ordinary inorganic acids. Magic acid (HSO3F–SbF5) is the strongest superacid known; many substances (such as H2SO4) can gain protons (i.e., be protonated) in magic acid. When SbF5 and HF are mixed in a molar ratio of 0.2:1, the acidity exceeds 10^9 times that of 100% sulfuric acid, and it further increases as the proportion of SbF5 rises. Magic acid – it would be more appropriate to call it magic acid – should be stored in containers made of polytetrafluoroethylene. In general, superacids refer to acids that are more acidic than 100% sulfuric acid. Application value: At present, superacids have great application value in chemistry and the chemical industry; they serve as both protonation reagents for inorganic and organic substances and as catalysts with extremely high activity. Many chemical reactions that were extremely difficult or even impossible to carry out under normal conditions can be achieved in an environment of superacidic substances. It was completed with exceptional smoothness. Due to the extraordinary acidity and corrosiveness of superacids, some chemical reactions that were previously extremely difficult or even impossible to carry out can now be performed smoothly under their influence. For example, n-butane can, under the action of superacidic substances, experience the breaking of carbon-hydrogen bonds to produce hydrogen; it can also have its carbon-carbon bonds broken to yield methane, or it can undergo isomerization to form isobutane – all of these reactions are impossible with ordinary acids. It is foreseeable that with the successive emergence of these superacids with exceptional acidity and corrosivity, chemistry and the chemical industry will rapidly enter a new era!

The strongest acid is a matter of debate… Some believe it to be perchloric acid, while others say that perchloric acid is not as acidic as hypochlorous acid; still others claim that teachers teach them that the strongest acid is aqua regia. Also... it’s called Magic Acid (SbF5·HSO3F), but it doesn’t seem to be an acid in the standard sense. Even if its acidity is 1 billion times that of concentrated sulfuric acid… Magmatic acid is a mixture composed of HSO3F and SbF5. The precise definition of an oxyacid is a substance consisting of O, H, and a central atom that can ionize protons on its own; the ratio with the strongest acidity is HSO3F:SbF5 = 2:98 (on a molar basis), and this is what is truly referred to as magmatic acid. If you study coordination chemistry, you will understand why magic acid is so strong an acid. The mechanism behind its high acidity is as follows: Firstly, HSO3F (fluorosulfonic acid) is inherently more acidic than HClO4. However, in aqueous solution, due to the leveling effect, their acidity levels are the same (just as nitric acid and hydrochloric acid solutions of the same concentration have similar acidity; we generally consider HNO3 and HCl to be indistinguishable in terms of acidity, but this is not actually the case). After HSO3F dissociates to release H+, the strong electron-withdrawing effects of oxygen and fluorine (inductive effect) cause the negative charge to be distributed more evenly throughout the ion. This reduces the Coulombic force exerted by the proton on the anion group, allowing the proton to be released more easily. Next is the role of SbF5. In (SO3F)−, the presence of a S→O coordination bond results in a significant negative charge on the oxygen atom. In SbF5, due to the inductive effect of fluorine on antimony, antimony carries a strong positive charge, and it possesses a 5p empty orbital (making it a strong Lewis acid). This orbital can form strong coordination bonds with the lone electron pairs on the oxygen atom in (SO3F)−, thereby creating a S→O→Sb bond structure. As a result, the negative charge is dispersed over a larger area, and it is well shielded by the SbF5 groups. At most, three SbF5 molecules can bind to one molecule of (SO3F)−; however, the lower the degree of binding, the more stable the compound is, as the large size of the SbF5 groups prevents them from bonding effectively with too many molecules of (SO3F)−. This explains why a relatively large amount of SbF5 is present in superacid; as a result, there is little Coulombic force exerted by H+ on this complex, allowing H+ to be quite free and even to form two-electron, three-center bonds with C-H bonds that have a higher electron density. Such bonds are unstable and tend to break down, producing carbocations and H2. If we use Arrhenius’ theory of ionization to define acids and bases, then superacid does not fit the standard definition of an acid. However, according to Brønsted’s theory of acids and bases based on protons, acids and bases are not limited to aqueous solvents. Superacid is actually formed by dissolving fluorosulfonic acid in antimony pentafluoride, and the presence of antimony pentafluoride increases its dissociation degree, making it the strongest acid known to date. Someone’s order is fluorsulfonic acid, perchloric acid, hydriodic acid, hydrobromic acid, sulfuric acid, hydrochloric acid, nitric acid, chloric acid, sulfurous acid, iodic acid, phosphoric acid, arsenic acid, nitrous acid, hydrofluoric acid, formic acid, carbonic acid, hydrosulfuric acid, hypochlorous acid, hydrocyanic acid, boric acid, silicic acid. Nitrosyl chloride was not included because it is not an acid; it merely possesses strong oxidizing properties. Manganese acid was not included either because it does not exist at all – under acidic conditions, manganeseate ions rapidly undergo disproportionation. As for permanganic acid, the acidic environment required is on the order of that of phosphoric acid. As for hydrofluoric acid, it is precisely because fluorine has a high electronegativity and the effective nuclear charge on hydrogen is low that fluorine strongly attracts hydrogen; the attraction between them is very strong, which leads to difficulty in dissociation. Moreover, the hydrogen atom in hydrogen fluoride does not possess strong oxidizing properties. If it is elemental fluorine, its oxidizing power should be very strong.

By strong acid here, it refers to its oxidizing power, right? If that’s the case, I think only acids that have been mixed together are the strongest, such as aqua regia