Pure sulfuric acid is generally a colorless oil liquid with a density of 1.84 g/cm³ and a boiling point of 337℃. It can be miscible with water in any proportion and release a lot of heat at the same time to make water boil. When heated to 290℃, sulfur trioxide begins to release and eventually becomes 98.54% aqueous solution, which boils at 317℃ and becomes an azeotrope. The high boiling point and viscosity of sulfuric acid are due to the strong hydrogen bonds within its molecules.Because of its high dielectric constant, sulfuric acid is a goodsolvent for electrolytes, but less ideal as a non-electrolyte solvent. The melting point of sulfuric acid is 10.371℃. Adding water or sulfur trioxide will decrease the freezing point

Metal oxidation and strong oxidizing properties

Dilute sulfuric acid has the properties of a general acid, and can react with active metals such as zinc (Zn), iron (Fe), manganese (Mn), nickel (Ni), aluminum (Al), magnesium (Mg), and release hydrogen (H2) , and does not react with inactive metals such as copper to generate hydrogen. Take iron as an example:

Fe(s) + H

2SO

4 (aq)→ H

2 (g) + FeSO

4 (aq)

However, concentrated sulfuric acid has strong oxidizing properties and can undergo redox reactions with many inactive metals. [9] Concentrated sulfuric acid is a strong oxidant. During the reaction, it is reduced to water and sulfur dioxide (SO2) instead of hydrogen, and the oxidation number of sulfur is reduced from +6 to +4. The strong oxidizing property of concentrated sulfuric acid is related to the presence of H2SO4 molecules in it.

2 H2SO4 + 2 e- → SO2 + 2 H2O + SO42-

Take copper as an example:

Cu + 2 H2SO4 → SO2 + 2 H2O + SO42- + Cu2+

If it is in contact with active metals, the concentrated sulfuric acid will be reduced to a greater extent, taking zinc as an example:

3 Zn + 4 H2SO4 → S + 4 H2O + 3 SO42- + 3 Zn2+

However, lead and tungsten can resist the corrosion of sulfuric acid because they form a protective layer when they react.

Oxidation of non-metallic substances

The strong oxidizing properties of concentrated sulfuric acid allow it to also oxidize nonmetals such as carbon and sulfur.

C + 2 H2SO4 → CO2 + 2 SO2 + 2 H2O

S + 2 H2SO4 → 3 SO2 + 2 H2O

In the above reaction, the oxidation number of carbon and sulfur increased from 0 to +4.

When sulfur and selenium are dissolved in oleum, they are gradually oxidized to polycations such as S162+ (orange yellow), S82+ (blue), S42+ (yellow), Se82+ (green), Se42+ (orange). [19]

react with certain salts

Sulfuric acid can react with soluble barium salts to produce barium sulfate precipitates and corresponding acids, and can react with carbonates to produce corresponding sulfates, water and carbon dioxide.

H2SO4 + BaCl2 → BaSO4↓ + 2HCl

Na2CO3 + H2SO4 → Na2SO4 + H2O + CO2↑

Electrophilic aromatic substitution reactions[edit]

Sulfuric acid can undergo electrophilic aromatic substitution reaction to become sulfonic acid. [20]

 existence in nature

 The water is the highly acidic Tinto River in Spain

100% pure sulfuric acid is a colorless viscous liquid that is difficult to find on Earth because it has a high affinity for water and absorbs it when exposed to air. Acid rain may contain dilute sulfuric acid. This is mainly because under the action of rainwater, sulfur dioxide in the atmosphere combines with water, and the product sulfurous acid is further oxidized to form sulfuric acid. As for sulfur dioxide in the atmosphere, it mainly comes from the exhaust gas emitted by many vehicles and the combustion of sulfur-containing fossil fuels.

In nature, many sulfur-containing minerals, such as iron sulfate, form sulfuric acid after an oxidation reaction, and the formed liquid is highly acidic, which can oxidize residual metals and release toxic gases.

It is also pointed out that in the biological world, there is a kind of sea slug (Notaspidean pleurobranchs) that can also spray secretions containing sulfuric acid to defend against enemies. 

Sulfuric acid can also be found in the upper atmosphere of Venus. This is mainly due to the photochemical action of the sun on sulfur dioxide, carbon dioxide and water. Ultraviolet photons with wavelengths shorter than 160 nanometers can photolyze carbon dioxide into carbon monoxide and atomic oxygen. Atomic oxygen is very reactive, it reacts with sulfur dioxide into sulphur trioxide. Sulfur trioxide further reacts with water to release sulfuric acid. Sulfuric acid is liquid in the higher and cooler regions of the Venusian atmosphere. This thick layer of sulfuric acid clouds about 45-70 kilometers away from the surface of the planet covers the entire surface of the planet. This layer of the atmosphere constantly releases acid rain.

On Venus, the formation of sulfuric acid is in a constant cycle. As the sulfuric acid is evaporated as it falls from higher, cooler regions of the atmosphere to lower, warmer regions, it contains less and less water and becomes more concentrated. When the temperature reaches 300 °C, sulfuric acid begins to decompose into sulfur trioxide and water, both products are gases. Sulfur trioxide is very active and decomposes into sulfur dioxide and atomic oxygen. The atomic oxygen then oxidizes carbon monoxide to carbon dioxide. The sulfur dioxide and water rise from the middle to the upper layers of the atmosphere where they react to release sulfuric acid and the process starts all over again. cycle.

Europa

Images from the Galileo probe show that sulfuric acid may also be present on one of Jupiter's moons, Europa, but the details are still debated. [twenty two]

Other methods

Before about 1900, the lead chamber method was the main method for the production of sulfuric acid. [23] As of the end of the 1940s, 50% of chemical plants in the United States still used the lead chamber method to produce sulfuric acid.

In ancient laboratories, sodium bisulfite was used to prepare sulfur dioxide, which was passed into hydrogen peroxide to produce sulfuric acid:

SO2 + H2O2 → H2SO4

The reaction of hydrogen sulfide and copper sulfate solution, the reaction of oxalic acid and copper sulfate (because the Ksp of copper oxalate is too small, the reaction is forced to pull) [source request], and the hydrolysis of sulfonyl chloride will produce sulfuric acid.

But in modern times, laboratories can usually buy sulfuric acid directly without preparation.

Use

World sulfuric acid production situation in 2000.

Sulfuric acid is an important industrial chemical used in a wide range of applications such as fertilizers, non-alkaline cleaners, skin care products, and paint additives and explosives. The importance of sulfuric acid can be reflected in its production volume. [24] As of 2004, the world produced nearly 1.8 billion tons of sulfuric acid, of which Asia accounted for 35%; North America (including Mexico) accounted for 24%; Africa accounted for 11%; Western Europe accounted for 10%; Eastern Europe and Russia accounted for 10% %; Australia and Oceania accounted for 7%; South America accounted for 7%. [25] In the total production, about 60% are used to make fertilizers, such as ammonium phosphate and ammonium sulfate; about 20% are used by chemical plants to make cleaning products, pharmaceuticals or other industrial purposes, such as catalysts for refining gasoline, etc. . [26]

General chemical use

The most widespread use of sulfuric acid is to make phosphoric acid, which is used to make phosphorus-containing fertilizers. 93% sulfuric acid is used to make calcium sulfate, hydrogen fluoride and phosphoric acid. Hydrogen fluoride will eventually be sequestered in the form of hydrofluoric acid.

Ca

5F (PO

4)

3 + 5H

2SO

4 + 10H

2O → 5 CaSO

4·2H

2O + HF + 3H

3PO

4

Another use of sulfuric acid is in papermaking. Sulfuric acid is used to produce aluminum sulfate, which reacts with a small amount of soap on the wood pulp fibers to form aluminum-containing carboxylates that solidify the fibers and create a harder surface.

Production of aluminum sulfate:

al

2O

3 + 3 H

2SO

4 → Al

2(SO

4)

3 + 3 H

2O

Sulfuric acid can also produce aluminum hydroxide, which is used to separate harmful substances in wastewater. Aluminum hydroxide is a very important chemical substance in sewage treatment plants. Also, sulfuric acid is an essential chemical in the manufacture of many dyes.

industrial cleaning products

Sulfuric acid is also an ingredient in many cleaning products used to remove oxides, rust, etc. Spent sulfuric acid is recycled by burning the acid with various organic substances to release sulfur dioxide and sulfur trioxide, which can be used to produce new sulfuric acid.

catalyst

Sulfuric acid is a catalyst for many chemical reactions. For example, it catalyzes the manufacture of nylon; in addition, several gasoline refining processes also require the catalysis of sulfuric acid.

electrolyte

Acid drain water contains high concentrations of sulfuric acid. The picture shows that a few drops of acidic drain water quickly turned the pH test paper red and eroded it, showing its strong acidity and dehydration.

Sulfuric acid is the electrolyte in automotive lead-acid batteries. The relevant chemical equations are:

anode:

Pb + SO2-

4 ⇌ PbSO

4 + 2 e-

cathode:

PbO

2 + 4 H+ + SO2-

4 + 2 e- ⇌ PbSO

4 + 2 H2O

Total equation:

Pb + PbO

2 + 4 H+ + 2 SO2-

4 ⇌ 2 PbSO

4 + 2 H2O

General household use

Most acidic waterway dredging products in the world contain sulfuric acid, [10][11] can remove hair, oil and other stasis. For safety reasons, use caution and wear gloves when handling. In addition, because sulfuric acid will have a high exothermic reaction with water, it is advisable to keep the channel as dry as possible before use, and slowly pour in the relevant dredging agent.

Laboratory risk

98% sulfuric acid will quickly corrode and carbonize the paper after contacting it, making it black.

A chicken paw was severely corroded and carbonized by high-concentration sulfuric acid within tens of seconds, showing the damage that sulfuric acid can do to skin and flesh.

Sulfuric acid (especially in high concentrations) can be extremely damaging to flesh. Like other corrosive strong acids and strong bases, sulfuric acid can quickly undergo amide hydrolysis and ester hydrolysis with proteins and fats, thereby decomposing biological tissues and causing chemical burns. However, its strong corrosiveness to the flesh is also related to its strong dehydration, because sulfuric acid can also dehydrate with carbohydrates in biological tissues and release a lot of heat energy. In addition to causing chemical burns, it can also cause second-degree flame burns. [8][9] Therefore, the damage caused by sulfuric acid is often greater than that of other comparable strong acids (such as hydrochloric acid and nitric acid). If sulfuric acid accidentally touches the eyes, the retina will be severely damaged and may cause permanent blindness; and if it is accidentally ingested, it will cause irreversible damage to internal organs and even be fatal. [6] Concentrated sulfuric acid is also highly oxidizing and will corrode most metals, so it must be stored carefully. [9]

The danger of sulfuric acid increases with increasing concentration. This is because in addition to the increase in the proportion of acidic substances, its dehydration and oxidation properties are also increasing. When the content of sulfuric acid in a solution is equal to or exceeds 1.5M, it should be affixed with a "corrosion" warning label, and between 0.5-1.5M, it is "irritating". However, even the "low concentration" sulfuric acid (about 1 M concentration, 10% specific gravity) commonly used in the laboratory will eat through the paper in a certain period of time.

theWhen concentrated sulfuric acid accidentally touches the skin, in order to avoid further damage to the skin by concentrated sulfuric acid, rinse the affected area with a large amount of flowing water for at least 10-15 minutes, because a large amount of water can quickly cool the damaged tissue and take away heat. The old textbooks believed that the concentrated sulfuric acid on the skin should be wiped off with a dry cloth before further treatment, but because the high-concentration sulfuric acid will quickly carbonize the flesh after contacting the skin, the damaged skin may be scratched with a dry cloth. However, if sulfuric acid is accidentally splashed on protective clothing, it should be taken off immediately and the affected area should be rinsed thoroughly. [27]

Because sulfuric acid and water will react violently and release heat energy, when diluting concentrated sulfuric acid, the acid should be poured into water instead of water into the acid, so that the high specific heat capacity of water can be used to reduce the acid splash due to high temperature boiling out of risk. Generally, in the laboratory, dilute sulfuric acid of 6 M (about 35% specific gravity) or higher is the most dangerous, because when this amount of sulfuric acid reacts with water, it can release enough heat to make the whole cup of solution boil.

Industrial risk

Although sulfuric acid is not flammable, it will release flammable hydrogen gas when it reacts with metals, which may cause an explosion. As a strong oxidant, concentrated sulfuric acid will release toxic sulfur dioxide when it undergoes redox reactions with metals, threatening work. personnel health. In addition, prolonged exposure to aerosols containing sulfuric acid (especially high concentrations) will severely irritate the respiratory tract and even lead to pulmonary edema. But the risk is reduced by the shorter exposure time.

In the United States, the maximum permissible exposure level (PEL) of sulfuric acid is set at 1 mg/m3, and this figure is similar in other countries. Ingesting sulfuric acid by mistake may lead to vitamin B12 deficiency, among which the spine is the most susceptible part.

Relevant

Sulfurous acid (H2SO3)

Peroxymonosulfuric acid (H2SO5)