Fluoroantimonic acid is the strongest superacid based on the measured value of its Hammett acidity function (H0), which has been determined for different ratios of HF:SbF5.

1. 8 Strongest Acids Ever
Known To Us
Prepared by - Rohan Jagdale

2. What makes an acid strong or weak? To answer this
question, we first need to look at the definition of an acid.
It is a chemical compound that accepts electrons and/or
donates (dissociate) hydrogen ions, also known as
protons.
Therefore, the acidity levels of an acid depend on its
ability to disassociate hydrogen ions, i.e., the higher the
number of hydrogen ions produced by the acid in a
solution more acidic it is.
Now, before we get on with the list of the strongest acids
on Earth, there are specific terms and definitions you first
need to get familiar with.

3. Acid dissociation constant (Ka):
Sometimes known as the acid-ionization constant or simply acid
constant is the quantifiable strength of an acid in aqueous
solution. On one hand, where pH or “power of hydrogen” specify
the level of basicity or, in this case, the acidity of any solution, acid
dissociation constant tells us about the concentration of hydrogen
ions [H+] or hydronium ions [H3O+] in a solution.
This brings us to another related and important acidity indicator
pKa. It is basically a negative integer logarithm of Ka
pKa = -log10Ka.

4. Acetic acid donates a proton (in green) to water to produce
hydronium ion and acetate ion. (Oxygen in red, hydrogen
is white and carbon in black)
The stronger the acid, the lower the pKa values.

5. Hammett acidity function: (Ho)
We all are aware of pH scale, which is widely used to measure
acidity or basicity levels of chemicals, but when it comes to
superacids, it simply becomes useless, since their acidity levels
are million times more than sulfuric acid and hydrochloric acid.
So in order to scale the superacids based on their acidity levels,
researchers came up with Hammett acidity function. It was
initially suggested by American physical chemist Louis Plack
Hammett.

6. Superacid
A superacid is simply an acid with an acidity
level of more than that of 100% sulfuric acid
with Hammett acidity function lower than -12. In
more technical terms, it can be defined as a
medium in which the chemical potential of the
proton is higher than that found in pure sulfuric
acid.

7. 8. Sulfuric Acid

9. ➔ Chemical Formula: H2SO4
➔ pKa value: -3
➔ Ho value: 12
➔ It is odorless, colorless and produces an
intense exothermic reaction when mixed
with water.

10. ➔ It is essential for multiple industries like
agriculture, wastewater treatment, and oil
refining. Sulfuric acid is also used in battery
acids and cleaning agents.
➔ H2SO4 can cause extensive damages to
human skin when it comes to direct contact.
It’s also highly corrosive to many metals.

11. 7. Hydrochloric acid

13. ➔ Chemical Formula: HCl
➔ pKa value: -5.9
➔ The hydrochloric acid was discovered sometime
around 800 AD by an Iranian polymath named
Jabir ibn Hayyan.
➔ Hydrochloric Acid (HCl) is a colourless to
yellowish-green, clear corrosive liquid with a
pungent, irritating odour.

14. Properties
● Molecular Weight: 36.5g/mol
● Boiling Point: 80°C(@conc.32%); 45C@conc.37%)
● Freezing Point: -42°C(@conc.32%); -29°@onc.37%)
● Vapor Pressure (at 20°C): 30hPa, at20°
(Concentration:32%), 200hPa, at20°
(Concentration:37%)
● Liquid Density (Water = 1.0): 1.16 – 1.19kg/m3 (@20°C)
● Vapor Density (Air = 1.0): 1.53kg/m3

15. Uses
➔ The uses for hydrochloric acid are numerous and include
steel pickling, corn syrup production, brine treatment, oil well
acidizing, Calcium Chloride production as well as swimming
pool treatment.
➔ hydrochloric is largely used in heavy industries to remove
rust from iron and steel before further processing. Moreover,
it is a vital component in the production of organic (vinyl
chloride used for PVC) and many inorganic compounds.

16. 6. Triflic Acid

18. ➔ Chemical Formula: CF3SO3H
➔ pKa value: -14.7
➔ Trifluoromethanesulfonic acid, most commonly
known as triflic acid, was first synthesized/discovered
by Robert Haszeldine, a British chemist back in 1954.
➔ It is known for its remarkable chemical and thermal
stability. Whereas other strong acids like nitric and
perchloric acids susceptible to oxidation, triflic acid is
not.

19. Uses
Triflic acid is used in many protonations and titrations (quantitative analysis
of a chemical’s composition). An important reason why triflic acid is
preferred in certain cases is that it doesn’t sulfonate other substances,
which is common with chlorosulfonic acid and sulfuric acid.
it’s extremely dangerous. Any skin contact with the acid can cause severe
burns and can have slightly delayed tissue damage. It can also cause
pulmonary edema and spasms and other critical conditions when inhaled.
Precautions

20. 5. Fluorosulfuric Acid

21. Fluorosulfuric acid

22. ➔ Chemical Formula: HSO3F
➔ Ho value: -15.1
➔ pKa value: -10
➔ Fluorosulfuric acid or sulfurofluoridic acid (official name) is the
second strongest single-component acid available today.
➔ It’s yellow in appearance and of course highly corrosive/toxic.
➔ HSO3F is generally produced by reacting hydrogen fluoride with
sulfur trioxide, and when combined with antimony pentafluoride,
it produces “Magic acid,” a far stronger acid and protonating
agent.

23. Uses
The acid can be used to alkylate hydrocarbons (with
alkenes) and isomerize alkanes, and for glass
etching (glass art). It’s a common fluorinating agent
in laboratories.

24. 4. Perchloric acid

25. 60% Perchloric acid | Image Courtesy: W. Oelen
Chemical Formula:
HClO4
pKa value: -10, -15.2

26. ➔ Chemical Formula: HClO4
➔ pKa value: -10, -15.2
➔ Perchloric acid is among the strongest known
Brønsted–Lowry acids, which have powerful oxidizing
properties and is highly corrosive.
➔ Traditionally, it’s produced by treating sodium perchlorate
with hydrochloric acid (HCl), which also creates sodium
chloride.
➔ NaClO4 + HCl → NaCl + HClO4
➔

27. Uses
its explosive nature, perchloric acid is widely used and
even preferred in certain types of syntheses. It is also an
important component of Ammonium perchlorate, which
is used in modern rocket fuel.

28. 3. Fluorinated Carborane acid

29. The generic structure of a carborane acid

30. Chemical Formula: H(CHB11F11)
Ho value: -18
pKa value: -20
Carborane acids are one of the strongest groups of
superacids known to humans, few of which are considered
to have a Hammett acidity function value as low as -18,
that’s more than a million times stronger acidity level than
pure (100%) sulfuric acid.

31. One such member of this group is Fluorinated
Carborane acid. While the existence of such a
chemical was initially reported in 2007, researchers
were able to study the full extent of its nature only in
2013. Before its discovery, the crown of strongest
Brønsted Acid went to a highly chlorinated version of
this superacid family.

32. Uses
Fluorinated Carborane is the only known acid which
can protonate (transfer of hydrogen ion) carbon
dioxide to produce Hydrogen-bridged cations. In
contrast, CO2 doesn’t go through any remarkable
protonation when treated with other superacids like
Magic acid and HF-SbF5.

33. Fluorinated carboxylic acids as powerful building blocks for the
formation of bimolecular monolayers†

34. 2. Magic Acid

35. Fluorosulfuric acid+antimony pentafluoride 1:1

36. ➔ Chemical Formula: FSO3H·SbF5
➔ Ho value: -23
➔ FSO3H·SbF5, most commonly known as Magic acid,
is produced by mixing fluorosulfuric acid and
antimony pentafluoride in a molar ratio of 1:1.
➔ This superacid system was first developed in 1966 by
researchers at the George Olah lab, Case Western
Reserve University in Ohio.

37. Uses
While Magic acid is generally used to stabilize carbonium
ions in solutions, it has few other important industrial
applications. For example, it can accelerate the
isomerization of saturated hydrocarbons and even
protonate methane, xenon, and halogens, all of which are
all weak bases.

38. The molecular structure of Fluoroantimonic acid

39. 1. Fluoroantimonic acid

41. ➔ Chemical Formula: H2FSbF6
➔ Hovalue: -15 (pure form), -28 (with >50 mol%)
➔ Fluoroantimonic acid is perhaps the strongest of all
known superacids based upon the Hammett acidity
function values.
➔ It’s produced by mixing hydrogen fluoride with
antimony pentafluoride generally in a 2:1 ratio. This
reaction is exothermic in nature.

42. Uses
This superacid has several essential applications
in the chemical engineering and petrochemical
industry. For example, it can be used to separate
methane and H2 from neopentane and isobutane
(both alkane), respectively.

43. Precautions
Unsurprisingly, H2FSbF6 is extremely corrosive and
can go through violent hydrolysis, when in contact
with water. Like most superacids, Fluoroantimonic
acid can eat right through the glass; therefore, it
must be stored in PTFE (polytetrafluoroethylene)
containers.

44. References
https://www.rankred.com/strongest-acids/
https://www.softschools.com/formulas/chemistry/perchloric_acid_formula/612/
http://www.chemspider.com/Chemical-Structure.1086.html
https://en.m.wikipedia.org/wiki/Fluoroantimonic_acid
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