How does H2SO4 make bonds

Structural formula
Surname sulfuric acid
other names

Sulfur (VI) acid, oil of vitriol, dihydrosulfate, monothionic acid

Molecular formula H2SO4
CAS number 7664-93-9
Brief description colorless, odorless, slightly viscous liquid[1]
Molar mass 98.08 g mol−1
Physical state liquid[1]
density 1.8356 g · cm−3 [1]
Melting point 10.38 ° C[1]
boiling point 279.6 ° C[1]
Vapor pressure

1.3 hPa[1] (145.8 ° C[1])


completely miscible with water[1]

safety instructions

0.1 mg m−3 (measured as the inhalable aerosol fraction)[1]


2140 mg kg−1 (Rat)

WGK 1 - slightly hazardous to water
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions.

sulfuric acid (according to IUPAC: Dihydrogen sulfate) is a colorless, viscous liquid and a strong, inorganic acid. It is one of the mineral acids and one of the 20 most important chemicals in the chemical industry. As a food additive, it has the number E 513. Dilute sulfuric acid is called dilute acid. Until the 19th century, sulfuric acid also had the common name vitriol oil (derived from vitriol), which is no longer used today.

The salts and esters of the sulfuric acid are called sulfates and hydrogen sulfates. The salty sulfates contain the sulfate ion (SO42−).

Extraction and presentation

In the past, sulfuric acid was produced using the vitriol process and the lead chamber process. Modern processes are the contact process and the double contact process that has been further developed from it.

The oldest process for the production of sulfuric acid is the vitriol process. It was used by alchemists in the 13th century. Vitriols are sulphates that can be thermally decomposed relatively easily, converting into sulfur trioxide and a metal oxide. Johann Rudolph Glauber (1604–1670) constructed the world's first sulfuric acid factory, which produced sulfuric acid around 1650 in Nordhausen (Harz) using this process.

In the contact process, production takes place in three steps, whereby elemental sulfur (S) and oxygen (O2) Sulfur dioxide (SO2) is pictured:

The sulfur dioxide is mixed with vanadium pentoxide (V2O5) as a catalyst, to sulfur trioxide (SO3) implemented:

Sulfur trioxide is the anhydride of sulfuric acid. Due to its low solubility in water, it is not discharged directly into water, but into concentrated sulfuric acid, by which it is absorbed very well.

The disulfuric acid formed is continuously diluted with water.


Sulfuric acid with the empirical formula H2SO4 is a strong acid (pKS1 = −3, pKS2, that corresponds to the pKS. of the hydrogen sulfate anion HSO4 = 1.9). As a strong inorganic acid, it is one of the mineral acids. Concentrated sulfuric acid is also a powerful oxidizer. It also has a hygroscopic effect and can therefore be used to dry gases and liquids. The distorted tetrahedral sulfuric acid molecule has a large dipole moment, the positive pole of which lies between the two OH groups.

Sulfuric acid forms an azeotrope with water. If 100% sulfuric acid is heated to the boil, sulfur trioxide evaporates until a concentration of about 98 percent by weight is reached. Conversely, dilute sulfuric acid can be brought to this concentration by boiling it out.

100% sulfuric acid is produced by introducing sulfur trioxide into about 98% by weight sulfuric acid until it is anhydrous. Sulfuric acid can also bind sulfur trioxide in large quantities, the resulting liquid is called oleum because its viscosity is quite high. Oleum consists of a mixture of sulfuric acid and polysulfuric acids (disulfuric acid: H.2S.2O7, Trisulfuric acid H2S.3O10, etc.) In the trade there are oleum with up to 65 wt .-% sulfur trioxide. Oleum is used in chemical reactions for sulfonation or, if necessary, to bind as much water as possible from the reaction. This can minimize the consumption of sulfuric acid and often maximize the yield.

To determine the concentration, the density of the sulfuric acid is measured. Concentration can thus be deduced directly from standard tables. For example, the state of charge of a car battery is determined (see also lead accumulator).

A great deal of heat is released when concentrated sulfuric acid is diluted. Therefore, appropriate precautions must be taken. It is important that always the acid the water is mixed in, so Not the water the acid! Otherwise explosive evaporation of the water can occur, causing the liquid to splash away in an uncontrolled manner; the danger is obvious. The donkey bridge to it: "First the water, then the acid, otherwise the monster will happen."

Meaning and use

Sulfuric acid is one of the most commonly produced chemicals. In 1997 more than 130 million tons were produced worldwide. The possible uses are very diverse. Sulfuric acid is used

In the food industry, sulfuric acid is used as a technical aid to produce modified starch and casein and to treat drinking water. It does not flow into the end product and is therefore not present or only in traces that are harmless to health. In the European Union, sulfuric acid does not have to be shown on the product packaging.

Dissolving potassium permanganate in sulfuric acid to saturation produces a dark green oily liquid (dimangan heptoxide), which is a powerful oxidizing agent. It immediately carbonizes organic substances such as wood and spontaneous combustion occurs with acetone or other combustibles. By dissolving potassium dichromate in sulfuric acid, chromosulfuric acid is obtained, an agent that was previously used for cleaning purposes in laboratories.

The amount of sulfuric acid produced was an indicator of the efficiency of a country's chemical industry. In the second development phase of the chemical industry, large amounts of sulfuric acid are consumed.

Development phases:

  • I. prevailing caustic soda consumption
  • II. Predominant sulfuric acid consumption
  • III. predominant chlorine consumption

Structure and relationships

In the sulfuric acid molecule, as in the hydrogen sulfate anion, the sulfur atom has a distorted tetrahedral coordination. The two S-O bonds to the OH groups are noticeably longer than to the two “naked” oxygen atoms. The bond lengths found correspond to bond orders of 1 or 2. In the frequently used notation with (covalent) double bonds and without formal charges, however, the bond of the four oxygen atoms to the sulfur cannot be explained without 3d orbitals of the sulfur for the π- Ties are used (see PSE). However, detailed theoretical considerations show that d orbitals contribute little to the bonding in main group element compounds. The shorter bond to the “naked” oxygen atoms is therefore better described as a covalent single bond, which is shortened by additional electrostatic interactions. The charge separation can be derived from the only mesomeric boundary structure that obeys the octet rule.


Sulfuric acid can be detected in the form of the sulfate anion. For example, precipitation as poorly soluble microcrystalline barium sulphate after the addition of barium chloride solution serves as sulphate detection.

Important connections




  1. abcdefGHi Entry on sulfuric acid in the GESTIS substance database of the BGIA, accessed on March 31, 2007 (JavaScript required)

See also

Categories: Corrosive Substance | Mineral acid | Sulfur compound | sulfate