H2SO3 also known as sulfurous acid is founded in the chemical compound that is found in the gas phase only. Sulfurous acid is a reducing agent as well as a bleaching agent.


:eight_pointed_black_star: About Sulfurous Acid (H2SO3)

:small_red_triangle_down: Fast Facts

Element Sulfurous acid
Chemical formula H2SO3
Molar mass 82.07 g/mol
Acidity (pKa) 1.857, 7.172
No. of hydrogen bond acceptor 4
No. of hydrogen bond donor 2
Conjugate base Bisulfite
Flashpoint Non-flammable

The chemical compound H2SO3 is sulfurous acid, also known as sulfuric(IV) acid, sulfurous acid in the United Kingdom, and sulfuric(IV) acid in the United Kingdom. Despite the lack of proof, sulfurous acid has been discovered in the gas phase. However, common anions, bisulfite (or hydrogen sulfite) and sulfite are the conjugate bases of this mysterious acid. Sulfurous acid is a chemical step in the process of sulfur dioxide into acid rain.

It will break down if you try to evaporate the solution to make waterless sulfuric acid (reversing the forming reaction). So2 is used in the cooling process. Sodium bisulfite and sulfite salt solutions are also utilized as reducing agents and disinfectants in aqueous sulfur dioxide solutions. Taking in another oxygen atom causes them to become sulfuric acid or sulfate.

This led us to calculate H2SO3’s infrared (IR) spectrum and compare it to the Galileo images of Io and Europa. We may infer that H2SO3 is present on Io and possibly to a lesser level on Europa based on the existing data.

:eight_pointed_black_star: Applications Of Sulfuric Acid (H2SO3)

  • It is utilized as an intermediate in a variety of sectors, such as chemical manufacturing.

  • Reducing agents are commonly used.

  • Disinfectants are one of its primary uses.

  • Paper is one of the many things that may be made using this material.

Humans have yet to discover and define sulfurous acid (H2SO3). This is owing to the high temperatures, high water content, and oxidizing environment of Earth’s atmosphere, which makes H2SO3 undesirable.

An analysis of H2SO3 using transition state theory found that it has a half-life of one day at 300 K, but at 100 K, this time is doubled. Cryogenic SO2 or SO2/H2O mixes and high-energy proton irradiation at temperatures about 100 K are likely necessary for the formation of H2SO3. Io and Europa, two of Jupiter’s moons, have similar climates.


It is non-flammable corrosive and poisonous. Sulfur dioxide solution can cause fatal injuries or death when inhaled, ingested, or come into touch with the skin. In its molten state, it poses a serious risk of serious burns to the skin or eyes. The chemical should thus be avoided by anyone with skin sensitivities. It produces corrosive, poisonous, and irritating fumes when it comes into contact with this substance.

:eight_pointed_black_star: Sulfurous Acid As Reducing Agent

Sulfurous Acid As Reducing Agent

The chemical substance H2SO3 is sulfurous acid, which is also known as sulphuric acid. Sulfurous acid has not been found in the solution, however, this molecule has been discovered in the gaseous phase.

However, common bisulfite (or hydrogen sulfite), anions, and sulfite are the conjugate bases of this mysterious acid. Sulfur dioxide dissolves in water to generate a weak and unstable acid. The presence of sulfur dioxide molecules in the gaseous phase cannot be explained, yet the chemical itself may be found in the solution.

As a bleaching agent, it is also a reducing agent. As a result, the sulfurous acid component cannot be separated in its purest form. Because H+ is converted to hydrogen gas H2, all Bronsted Lowry acids (proton donors) are considered oxidizing agents.

Sulfuric H2SO4, nitric, chromic, chloric, and perchloric acids, which generate an anionic form of oxygen, tend to be powerful oxidizing acids. Furthermore, phosphoric acid is a poor oxidizing acid because of its strong affinity for oxygen. Even less reactive metals like copper, where the H+ cation is not converted to hydrogen gas, can be reacted with by the oxidizing acids indicated above.

:eight_pointed_black_star: H2SO3 Composition

H2SO3 Composition

Hydrogen, sulfur, and oxygen are the three components that make up this complex molecule. The chemical formula reveals that there are a total of two hydrogen atoms, one sulfur atom, and three oxygen atoms in the compound in question. Sulfurous acid is the chemical name for the H2SO3 component.

The chemical structure of this acid is given. It demonstrates that a single sulfur atom is attached to two hydroxyl atoms OH and a single oxygen atom through the formation of a single bond. This demonstrates that the sulfur atom is directly connected to the oxygen atom in the hydroxyls, which are represented by the symbol OH.

:small_red_triangle_down: Hydrogen

The lightest element is hydrogen. Hydrogen is a diatomic gas with the formula H2. Not only is it non-toxic but it is also extremely flammable.

Hydrogen is the most abundant chemical in the universe, making up nearly 75% of all matter. The Sun is made up of mostly plasma hydrogen. Most hydrogen on Earth is in the form of water or organic molecules. Each atom of 1H has one proton, one electron, and no neutrons.

Hydrogen is nonmetallic and forms a single covalent link with most nonmetallic elements, generating water and practically all organic molecules. Because acid-base interactions frequently entail proton exchange between soluble molecules, hydrogen is vital.

When used in ionic compounds, hydrogen can be either a negatively charged (anion) or positively charged (cation) species, represented by the symbol H+. The H+ cation is a proton (symbol p), but in aqueous solutions and ionic compounds, it is charged by surrounding polar molecules or anions.

Because the Schrödinger equation can only be solved analytically for hydrogen, its energetics and chemical bonds have been studied extensively in the development of quantum mechanics.

:small_red_triangle_down: Sulfur

Today, practically all elemental sulfur is generated by decontaminating natural gas and petroleum. Sulfur is in matches and pesticides. Organosulfur compounds give out odors like odorized natural gas, skunk aroma, grapefruit, and garlic. Rotting eggs and other biological processes emit hydrogen sulfide.

Organosulfur compounds or metal sulfides are sulfur compounds that are crucial to all life. Organosulfur compounds include three amino acids and two vitamins (biotin and thiamine).

Others, like glutathione and thioredoxin, include sulfur. S–S linkages provide keratin, the protein found in the outer skin, hair, and feathers, its strength, and insoluble nature. Sulfur is an essential macronutrient for all living creatures and is required for metabolic activity.

:small_red_triangle_down: Oxygen

It is a highly reactive nonmetal that rapidly forms oxides with most elements as well as other compounds. Many important groups of organic molecules in living beings include oxygen atoms, such as proteins, nucleic acid, carbohydrates, and lipids, as well as the principal component inorganic compounds of animal shells, teeth, and bones. Oxygen is a component of water, which is the main ingredient of lifeforms.


Oxoacids such as sulfurous acid are capable of donating two protons (H+), which makes them useful as proton donors. Despite this, it is nevertheless classified as a weak acid since it is unable to entirely dissociate from the ions with which it interacts. The cause for this is due to the attachment of its bisulfite ion HSO3 to its proton, which is a chemical reaction.

:eight_pointed_black_star: Properties Of Sulfurous acid

Properties Of Sulfurous acid

  • Sulfurous acid Formula: As a weak inorganic acid, sulfurous acid (also known as sulfuric acid) is regarded to be an aqueous solution of sulfur dioxide in water.

  • Formula and structure: Sulfurous acid has the chemical formula H2SO3 and has a molar mass of 82.07 g/mol. Its molar mass is the same as that of water. It is made up of a sulfur atom that has formed two single bond with hydroxyl groups and one double bond with oxygen in the presence of other elements.

  • Occurrence: It is found naturally in nature as an intermediate product in the creation of acid rain, which is caused by the interaction of sulfur dioxide with moisture in the surrounding atmosphere.

  • Uses: Sulfurous acid is used as reducing agents and disinfecting agents. It can also be used as a moderate bleaching agent in situations involving chlorine-sensitive materials, according to the manufacturer.

  • Health hazards: Sulfuric acid is not commercially accessible as a free agent, and as a result, the health risks associated with it are not very significant. However, it decomposes quickly and releases hazardous sulfur dioxide gas into the environment.

  • Preparation: Sulfuric acid is made by dissolving sulfur dioxide in water and then boiling the solution. Although the reaction is reversible, the acid easily decomposes back into the reactants after it has completed.

  • Physical properties: Sulfuric acid is a colorless liquid with a harsh odor that is difficult to describe. It has a density of 1.03 g/mL and a boiling point of -60 °C, making it a very dense liquid.

  • Chemical properties: Sulfuric acid is a highly unstable compound that has never been isolated in its pure form. It decomposes quickly, releasing water and sulfur dioxide into the environment. When it is exposed to air, it also produces sulfuric acid. Sulfurous acid is a dibasic acid with mild acidity. It combines with bases to generate bisulfite and sulfite salts, which are harmful to the body.

Furthermore, when exposed to air, it produces sulfuric acid, which is a poisonous, powerful, and corrosive acid with a short half-life. As a result, exposure to sulfurous acid by inhalation, ingestion, or skin contact can result in severe burns, eye damage, and respiratory issues.

In this way, sulfurous acid is seldom found in its acid form but is more typically found in the form of its sodium or potassium salts, respectively. In the reaction described below, sodium sulfate is added to a solution of sulfur dioxide in water, resulting in the formation of the stable sodium bisulfite salt as a byproduct.

:eight_pointed_black_star: Lewis Structure Of Sulfurous Acid (H2SO3)

It is possible to depict Lewis’ structural formula as a representation that indicates how each atom is bound, as well as the lone electron pairs in each atom, using mathematical symbols. If you’re developing the Lewis structure of any compound, there are a few rules you need to remember:

  • The center atom is the atom having the lowest electronegativity among the group of elements.

  • The electronegativity increases from left to right and decreases from top to bottom

  • Hydrogens are never the primary constituents of an atom.

  • In oxoacids, hydrogens are always covalently linked to oxygens.

Covalent bonds are formed by sandwiching two electrons between each atom. Alternatively, you may just draw the covalent link between each atom. Each bond is made up of two electrons, one on each side.

Distribute the remaining 14 valence electrons among the atoms in their appropriate positions. Completion of the octet requires recalling the maximum number of electrons that may be held by each atom in its outermost shell.


It demonstrates that there are a total of six bonds. H2SO3 contains a total of 26 valence electrons in its structure. Twelve of the twenty-six atoms have already been utilized in the formation of bonds between the atoms in question. That is, 14 of the 26 valence electrons are occupied.

:eight_pointed_black_star: Significance Of Sulfur

Worldwide, salinity is a significant abiotic stressor for plant development and yield. Photosynthesis, growth, and development of plants are affected by ionic/osmotic impacts, nutritional imbalance, or oxidative stress when plants are exposed to high salt concentrations.

To counteract the negative effects of salt, plants employ a variety of strategies. Mineral nutrient status management in plants can be an effective defensive strategy against the consequences of salt stress, and it is one of several probable mechanisms. An essential plant nutrient, sulfur (S) is involved in the growth and development of plants.

After nitrogen, phosphorus, and potassium, it is ranked as one of the most essential elements. Vitamins, coenzymes, phytohormones, and reduced sulfur compounds all include this nutrient, which is crucial in understanding plant development and vigor under ideal and stressful conditions.

Increasing our knowledge of how salt affects plant physiology and metabolism, as well as the role sulfur plays in salt tolerance, is the subject of this paper.

:small_red_triangle_down: Sulfur Deficiency Symptoms

A sulfur deficit in plants causes leaf yellowing that is very similar to nitrogen shortage. Symptoms appear first on the young leaves and then spread to the elder leaves when sulfur levels drop too low.

The oldest leaves at the bottom of a plant that is deprived of nitrogen are the first to be damaged, progressing upwards. Gypsum deposits in the soil layers can trap sulfur, allowing older plants with extensive roots to re-establish themselves.

Sulfur has a major part in the growth of mustard crops, which will show signs of deficiency early on. It’s fairly uncommon for professional growers to rely on plant tissue testing to detect soil deficiencies.

:small_red_triangle_down: Sulfur Sources For Plants

Fertilizers and pesticides are the primary means through which sulfur is transported through the soil. In addition to fertilizer, manure is a major source of sulfur for plants.

  • Sulfur is found in plants in a 10:1 ratio, and it is stored in the plant’s tissues. Soil spontaneous decomposition and past plant debris provide a large portion of this.

  • Sulfur is released as minerals break down in the soil, and this sulfur is present in some minerals. Sulfur in the atmosphere is a less evident sulfur source for plants. Sulfur dioxide is a byproduct of the combustion of fossil fuels, which plants absorb during respiration.

  • One to three tonnes of sulfur per acre is all that plants require. While sulfur is a soil conditioner, it also functions as a buffer against the buildup of salt in the soil. The plant sulfur found in mustard, onions, and garlic contributes to the taste of these foods.

However, if the soil is sandy or overused, sulfur from fertilizer can build up and impede the generation of oil from the seeds. As a soil conditioner, sulfur needs between 1,000 and 2,000 pounds (450-900 kg.) per acre to lower salt levels (4,000 square meters). Fertilizer treatments are common, however, soils that do not effectively percolate are more likely to have sulfur shortages.

:small_red_triangle_down: Sulfur In High pH Soils

Those who garden in regions with low rainfall and little limestone tend to have acidic soil. It’s essential to reduce the pH level of the soil since most plants prefer it that way. It’s possible to employ sulfur for this, but it’ll be contingent on the pH of the solution.

To mildly acidify your soil, you might use a pH calculator provided by the National Gardening Association. Sulfur in its purest form can be found in fungicides or as a simple soil amendment in the form of finely milled sulfur.

:small_red_triangle_down: Sulfur Gardening Usage

Home landscapes don’t often require sulfur. Sulfur-depleted plants may benefit from a side dressing of manure. Slowly releasing sulfur into the soil by composting will not harm the plants. A sulfur application, whether in the form of sulfur dust or insecticides, is almost always advised for seed oil crops.

Sulfur is a common ingredient in most fertilizers, so the soil may be replenished. When using sulfur in the garden, use caution and pay attention to the manufacturer’s recommendations. Sulfur retention in soils can lead to problems with nutrient absorption. Use natural products and begin with little doses.


Sulfur, like phosphorus, is a vital mineral that cannot be omitted. Sulfur’s effect on plants is unknown. The presence of sulfur in plants aids in the synthesis of enzymes and proteins essential to plant life. Deficiencies can lead to major plant health issues and a loss of vigor, even at little levels.

:eight_pointed_black_star: Health Hazards Of Sulfurous Acid

A caustic, noncombustible, and poisonous chemical, sulfuric acid is a byproduct of sulfur production. Ingestion, inhalation, or skin contact with the chemical solution results in severe damage that ultimately results in death. molten sulfuric acid may cause serious burns to the skin and eyes when applied directly to the skin.

As a result, it is recommended that this substance not come into contact with the skin. It also releases poisonous, unpleasant, and corrosive gases into the atmosphere.

The following chronic (that is, long-term) health problems can occur at any time after exposure to sulfurous acid and can remain for months or even years after the exposure to sulfurous acid:

  • Cancer Risk - According to the most recent information available to the New Jersey Department of Health and Senior Services, sulfuric acid has not been studied to determine whether or not it can cause cancer in humans or animals.

  • Reproductive Hazard - Sulfuric acid compound has not been tested to see whether it can cause birth defects or other reproductive harm.

  • Long-Term Effects - Other long-term effects of sulfuric acid include irritation of the lungs and respiratory tract infections. Repeated exposure can result in the development of bronchitis, which manifests itself as phlegm, cough, and/or shortness of breath.


Sulfuric acid can cause severe irritation and burning of the skin and eyes, with the possibility of permanent eye damage. Sulfurous acid can irritate the nose and throat when inhaled. Breathing Sulfurous Acid can irritate the lungs, resulting in coughing and/or difficulty breathing.

Frequently Asked Questions - FAQs

People asked many questions about sulfurous acid. We discussed a few of them below:

:one: What is the origin of the name “sulfurous acid” for H2SO3?

Hydrogen, sulfur, and oxygen combine in this chemical to form the triatomic complex it is. Two hydrogen atoms, one sulfur atom, and three oxygen atoms make up the molecule, according to the molecular formula.

:two: Is sulfur toxic to humans?

Sulfur is largely non-toxic to humans, producing mainly moderate local irritation to the eyes, nose, throat, and upper respiratory tracts. However, it has the potential to emit harmful gases such as hydrogen sulfide or sulfur dioxide under certain conditions.

:three: How is H2SO4 formed?

industrially produced sulfuric acid is manufactured by reacting water with sulfur trioxide (see sulfur oxide), a chemical compound formed by the interaction of sulfur dioxide and oxygen either via contact or chamber method.

:four: Is battery acid a source of lead poisoning?

Lead-acid battery (LAB) use has increased dramatically in Bangladesh as the number of automobiles has increased. As a result, LAB production is on the rise. Lead utilized in these businesses primarily originates from LAB recycling. Employees in the LAB sector have the danger of being exposed to lead, which can result in lead poisoning.

:five: What is the processes involved in making oleum?

Production. Conversion of sulfur to sulfur trioxide in the contact process produces oleum, which is then dissolved in concentrated sulfuric acid. To regenerate sulfuric acid, a portion of the oleum must be diluted.

:six: What is the chemical name for H2SO4?

Water-soluble sulfuric acid (H2SO4) is a potent mineral acid that may be used in a variety of applications. In addition to being caustic, this colorless, oily liquid is also known as oil of vitriol. The chemical formula for sulfuric acid Mineral acid C2H4 is water-soluble.

:seven: How does your skin react to the smell of sulfur?

Inhaling sulfur dioxide vapor can cause skin irritation or burns, so be careful when you’re around it. Sulfur dioxide liquid is extremely cold and can cause severe injury to the eyes or frostbite to the skin.

:eight: Which chemicals do sulfur often react with?

There are no aromas or tastes associated with pure sulfur. It is a hard and brittle solid that is yellowish-white in color; it is also a poor conductor of electricity. Sulfides are formed when it interacts with all metals other than gold and platinum, and it also reacts with several nonmetallic elements to produce compounds.

:nine: Sulfuric acid has what kind of dangers?

Corrosive sulfuric acid (H2S04) damages the skin, eyes, teeth, and lungs when inhaled. A fatal outcome is possible in the event of an extremely high level of exposure. Sulfuric acid can be dangerous to workers. Dose, duration, and type of employment all affect the degree of exposure.

:keycap_ten: What is H2CO3 used for?

Hydrogen, carbon, and oxygen are the three components that make up carbonic acid (H2CO3). Small quantities of carbonic acid (H2CO3) are generated whenever carbon dioxide (CO2) reacts with its anhydride. Caves and cave formations like stalactites and stalagmites may be traced back to carbonic acid, which was a component in their development.

:closed_book: Conclusion

H2SO3 is the chemical formula for sulfuric acid. In the gas phase, sulfuric acid has been found; no indication of its presence in solution has been found. However, bisulfite and sulfite are the acid’s conjugate bases, which are common anions. An essential plant nutrient, sulfur (S) is involved in the growth and development of plants. After nitrogen, phosphorus, and potassium, it is ranked as one of the most essential elements.

Vitamins, coenzymes, phytohormones, and reduced sulfur compounds all include this nutrient, which is crucial in understanding plant development and vigor under ideal and stressful conditions. Sulfur-containing proteins are broken down by soil organisms into their amino acids. Another group of soil bacteria converts the amino acids’ sulfur to hydrogen sulfide (H2S). Sulfur bacteria break down H2S to sulfur and sulfate in the presence of oxygen. H2S is formed when sulfate oxidizes.

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