Hyposulfurous Acid Formula – Structure, Properties, Uses, Sample Questions

Hyposulfurous acid contains two Hydrogen (H), one sulfur (S), and two Oxygen (O) atoms. Hydrogen (H) is a chemical element that has atomic number 1 in the periodic table. Sulfur (S) is a chemical element with the atomic number 16 in the periodic table. Oxygen (O) is the chemical element with atomic number 8 in the periodic table. Let’s discuss Hyposulfurous acid.

Hyposulfurous Acid Formula 

Hyposulfurous acid contains two Hydrogen (H), one sulfur (S), and two Oxygen (O) atoms. It is an unstable oxoacid of Sulfur (S). It is an intermediate oxidation state between dithionous acid and hydrogen sulfide. It has two Hydroxy groups (OH), which are attached to the Sulfur (S) atom. It is also known as Sulfoxylic acid or Sulfur Dihydroxide or dihydroxidosulfur or sulfanediol. The chemical formula of Hyposulfurous acid is H₂SO₂.

Structure of Hyposulfurous acid

It contains two Hydroxy groups (OH), which are attached to the Sulfur (S) atom. In which sulfur has a +2 oxidation state.

Preparation of Hyposulfurous acid

• Hyposulfurous acid can be found in the gas phase. It is found as an intermediate acid by the oxidization of Hydrogen Sulfide in the natural environment.
• It can also be prepared by ultraviolet irradiation of a mixture consisting of solid H₂S and H₂O. This process takes place in circumstellar disks or comets.
• It can also be prepared by conducting ultraviolet irradiation on solid sulfur dioxide and hydrogen sulfide. 

Physical Properties of Hyposulfurous acid

• The Molecular weight of Hyposulfurous acid is 66.07 g/mol.
• It has Bisulfoxylate (SO₂H^–) and a conjugate base.
• It is an isomer of sulfinic acid.
• It has a pKa of  7.97.

Chemical Properties of Hyposulfurous acid

• Hyposulfurous acid disproportionates into Sulfur (S) and Hydrogensulfite (HSO₃^–), which in turn reacts to form thiosulfate (S₂O₃^2-).
• Hyposulfurous acid is oxidized to sulfur dioxide (SO₂), and it forms Diothionite (S₂O^2-₄).

2 SO₂^2- ⇌  S₂O₄^2-

• Hyposulfurous reacts with dithionite to form Hydrogen Sulfite (HSO^–₃) and Sulfur (S).

H₂SO₂ + S₂O₄^2- ⇢  2HSO₃^– + S.

• Hyposulfurous acid reacts with hypochlorite, bromine, or chlorine dioxide. It forms hydrogen sulfite and sulfates.

Uses of Hyposulfurous acid

• It is used as a reducing agent.
• It is used as a bleaching agent, which is used to bleach the pulp of paper.
• It is used in the dyeing process. 
• It is used in organic reactions, in which it is used to reduce the Nitro group to the Amino group.
• It is also used in industrial processes such as Sulfonating agents or Sodium ion sources.
• It is used in the textile industries and leather industries.
• It is used in food, photography, and polymer industries.

FAQs on Hyposulfurous acid 

Question 1: What happens when Hyposulfurous acid reacts in water with sodium hydroxide?

Answer:

When Hyposulfurous acid and Sodium Hydroxide (NaOH) reacts in water, we get Sodium Hyposulfite (Na₂SO₂) and Water (H₂O).

H₂SO₂ + 2NaOH ⇢ Na₂SO₂ + 2H₂O.

Question 2: What are the health hazards of Hyposulfurous acid?

Answer:

Health Hazards

• It gets heated on contact with air and moisture. This heat is used to ignite the surrounding combustible material.
• Exposure to fire or heat may rupture violently.

Question 3: Is Hyposulfurous acid or base?

Answer:

Hyposulfurous acid is a acid which is an unstable oxoacid of Sulfur (S). It is an intermediate oxidation state between dithionous acid and hydrogen sulfide.

Question 4: Write the reaction of Hyposulfurous acid with Oxygen.

Answer:

When Hyposulfurous acid reacts with Oxygen (O₂), we get Sulphur Dioxide (SO₂) and water (H₂O).

2H₂SO₂ + O₂ ⇢ 2SO₂ + 2H₂O.

Question 5: Write the reaction of Hyposulfurous acid Calcium Hydroxide.

Answer: 

When Hyposulfurous acid reacts with Calcium Hydroxide (Ca(OH)₂), we get Calcium Hydride (H₂Ca) and Sulfate Hydroxide (SO₄(OH)₂).

H₂SO₂ + 2Ca(OH)₂ ⇢ 2H₂Ca + SO₄(OH)₂

Question 6: Write the reaction of Hyposulfurous acid with Hydrogen Iodide.

Answer: 

When Hyposulfurous acid with Hydrogen Iodide (HI), we get Hydrogen Sulfide (H₂S), Iodine (I₂) and Water (H₂O).

H₂SO₂ + 4HI ⇢ H₂S + 2I₂ + 2H₂O.

Question 7: Write the reaction of Hyposulfurous acid with Hydrogen Sulfide.

Answer: 

When Hyposulfurous acid with Hydrogen Sulfide (H₂S), we get Water (H₂O) and Sulfur (S).

H₂SO₂ + H₂S ⇢ 2S + 2H₂O.