Hydrogen Peroxide - A Colorless Liquid Soluble in Water

October 14, 2025

Hydrogen peroxide is an aqueous solution with a concentration of 20%, but when stabilized, its concentration can reach up to 60%. In the industrial sector, hydrogen peroxide is used as a bleaching agent for textile raw materials due to its high concentration.

Hydrogen peroxide solution is a colorless liquid that is soluble in water. At high concentrations, it can decompose rapidly when it comes into contact with most common metals and compounds.

What Is Hydrogen Peroxide?

Hydrogen peroxide (H₂O₂) is a compound consisting of two hydrogen atoms and two oxygen atoms. It is a clear liquid with a slightly more viscous texture than water.

In the industrial sector, hydrogen peroxide is used as a bleaching agent for textile and paper raw materials at high concentrations. Structurally, hydrogen peroxide is an aqueous solution with a concentration of 20%, but when stabilized, its concentration can be as high as 60%.

Structure of Hydrogen Peroxide

Hydrogen peroxide contains two oxygen atoms, each of which has two pairs of unshared electrons. This results in the application of the valence shell electron pair repulsion (VSEPR) theory.

The hydrogen atoms repel the unshared electron pairs around the oxygen atoms, resulting in a bent molecular shape. Therefore, hydrogen peroxide has a bond angle of approximately 109.5°.

In its crystalline form, this angle is reduced due to hydrogen bonding within the molecules.

Physical and Chemical Properties of Hydrogen Peroxide

a. Physical Properties

Hydrogen peroxide solution is a colorless liquid that is soluble in water. At high concentrations, it can decompose rapidly when it comes into contact with most common metals and compounds.

Hydrogen peroxide is flammable and can decompose when exposed to fire or prolonged heat.

In its pure form, hydrogen peroxide is an almost colorless liquid.
It melts at 272.4 K and has an extrapolated boiling point of 423 K.
It is miscible with water in all proportions and can form hydrates.

b. Chemical Properties

Hydrogen peroxide acts as both an oxidizing agent and a reducing agent in acidic and alkaline media.

Oxidation Reactions of H₂O₂

Hydrogen peroxide oxidizes black PbS to white PbSO₄.

PbS + 4H₂O₂ → PbSO₄ + 4H₂O

It oxidizes KI to iodine.

2KI + H₂O₂ → 2KOH + I₂

It oxidizes nitrite to nitrate.

NaNO₂ + H₂O₂ → NaNO₃ + H₂O

It oxidizes acidified potassium ferrocyanide.

2K₄Fe(CN)₆ + H₂SO₄ + H₂O₂ → 2K₃Fe(CN)₆ + K₂SO₄ + 2H₂O

It oxidizes sulfite to sulfate.

Na₂SO₃ + H₂O₂ → Na₂SO₄ + H₂O

It oxidizes CrO₄²⁻ in an acidic medium to chromium peroxide (CrO₅).

CrO₄²⁻ + 2H⁺ + 2H₂O₂ → CrO₅ + 3H₂O

Bleaching Reaction

Hydrogen peroxide bleaches materials through oxidation. H₂O₂ can be used to bleach silk, wool, cotton, and hair.

H₂O₂ → H₂O + [O] Nascent oxygen

Colored substance + [O] → Colorless substance

Reduction Reactions of Hydrogen Peroxide

Hydrogen peroxide reduces barium peroxide to barium monoxide.

BaO₂ + H₂O₂ → BaO + H₂O + O₂

It also reduces ozone to oxygen.

O₃ + H₂O₂ → H₂O + 2O₂

It reduces alkaline potassium ferricyanide.

2K₃Fe(CN)₆ + 2KOH + H₂O₂ → 2K₄Fe(CN)₆ + 2H₂O + O₂

Advantages of Hydrogen Peroxide

Hydrogen peroxide can act against highly resistant microorganisms, such as bacterial spores and protozoan cysts, as well as infectious proteins such as prions. Other advantages include its toxicity profile and environmental characteristics.

However, the safety and effectiveness of hydrogen peroxide generally depend on how it is used, particularly its concentration.

Applications of Hydrogen Peroxide

Hydrogen peroxide is used in the production of acetone, antichlor agents, antiseptics, benzoyl peroxide, buttons, disinfectants, pharmaceuticals, hats, plastic foam, rocket fuel, sponge rubber, and pesticides.

If you are exposed to hydrogen peroxide, take the following first-aid measures.

a. Assisting in Breathing for A Person Which has Difficulty on Breathing

If the person has difficulty breathing, provide oxygen to assist breathing. If the person stops breathing, administer artificial respiration and seek immediate medical attention.

b. Remove Contact Lenses

If the person is wearing contact lenses, remove them and flush the eyes with water for 15 minutes. Seek medical attention for further examination and treatment.

c. Rinse the Skin with Water

Rinse the affected skin with water and cover it with an emollient. Remove any contaminated clothing. In cases of severe exposure, use disinfectant soap and antibacterial cream and seek medical attention.

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