A covalent single oxygen-oxygen bond connects the two hydroxyl groups that make hydrogen peroxide, which is an organic peroxide. It has an additional oxygen atom in its molecule, which makes it an unstable chemical compound. It is a chemical compound with the molecular formula H2O2. It has a greater viscosity than water and a pale blue hue in its pure form. It is the simplest peroxide with a single bond, i.e., an oxygen-oxygen bond.
As an unstable compound, hydrogen peroxide decomposes when exposed to heat, bases, or catalysts. When exposed to light, hydrogen peroxide decomposes very slowly. However, in the presence of the reactive compound, it decomposes very fast. Therefore, it is stored in a slightly acidic solution with a stabilizer.
Discovery Of Hydrogen Peroxide
- In 1799, Alexander von Humboldt reported the first synthesis of peroxide, i.e., barium peroxide, as a by-product of his attempts to decompose air.
- Louis Jacques Thénard, a French chemist, discovered hydrogen peroxide in 1818 while combining barium peroxide and nitric acid.
- In 1892, the Italian physical chemist Giacomo Carrara determined its molecular weight by using freezing point depression, which confirmed that its molecular formula was H2O2.
- Pure hydrogen peroxide was obtained in 1894 when Richard Wolfenstein produced it through vacuum distillation.
- The English mathematical physicist William Penney and the Scottish physicist Gordon Sutherland proposed a molecular structure for hydrogen peroxide in 1934 that resembled the currently accepted molecular structure.
Properties Of Hydrogen Peroxide
|Molar Mass||34.0147 g/mol|
|Melting Point||−0.43 °C (31.23 °F; 272.72 K)|
|Boiling Point||150.2 °C (302.4 °F; 423.3 K) decomposes|
Physical Properties Of Hydrogen Peroxide
- Hydrogen peroxide appears blue-pale in its pure form.
- Its boiling point has been extrapolated to a temperature as high as 150.2 °C, which is almost 50 °C higher than the boiling point of water.
- H2O2 is thermodynamically unstable.
- It is soluble in water, alcohol, and ether in all proportions.
- H2O2 is a thick slurpy liquid in its pure form.
- It is diamagnetic with both polar and nonpolar bonds.
- H2O2 forms a homogeneous mixture of water in all proportions and forms hydrates.
- H2O2 has a slightly bitter taste and sharp odor.
Chemical Properties Of Hydrogen Peroxide
- Decomposition caused by light: Light exposure decomposes H2O2. Therefore, it is stored in wax-lined glass or plastic containers with urea as a stabilizer.
H2O2 (l) → H2O (l) + O2 (g) [when exposed to UV]
- Auto-oxidation and auto-reduction: Hydrogen peroxide (H2O2) is an unstable liquid in its purest state. It decomposes into water and oxygen when left out for a long time or heated.
- Pure hydrogen peroxide is unstable, so it decomposes in water and oxygen.
2 H2O2 (aq) → 2 H2O (l) + O2 (g)
- When blue litmus reacts with hydrogen peroxide, it turns red.
- Hydrogen peroxides’ neutralization reactions with hydroxides demonstrate their acidic nature.
- When sodium hydroxide, NaOH, reacts with hydrogen peroxide, H2O2,
NaOH +H2O2 → NaHO2 + H2O
- Acidic ferrous sulfate (2FeSO4) oxidizes to ferric sulfate (Fe2 (SO4)3) in an acidic medium when reacted with hydrogen peroxide (H2O2).
2 FeSO4 + H2SO4 + H2O2 → Fe2(SO4)3 + H2O
- Sodium nitrite (NaNO2) is oxidized to sodium nitrate (NaNO3) when reacted with hydrogen peroxide (H2O2).
NaNO2 + H2O2 → NaNO3 + H2O
- Sodium sulfite (Na2SO3) is oxidized to form sodium sulfate (Na2SO4) when it reacts with hydrogen peroxide (H2O2).
Na2SO3 + H2O2 → Na2SO4 + H2O
- Hydrogen peroxide oxidizes black Pbs to lead (II) sulfate, PbSO4 (white-solid).
Pbs + 4 H2O2 → PbSO4 + 4 H2O
- In the presence of other oxidizing agents, hydrogen peroxide acts as a reducing agent. This is because it can take up oxygen to make water and oxygen gas.
Examples of Hydrogen Peroxide Acting as a Reduction Agent
- Hydrogen peroxide reduces barium peroxide (BaO2) to monoxide (BaO).
BaO2 + H2O2 → BaO + H2O + O2
- H2O2 reduces alkaline potassium ferricyanide.
2 K3Fe(CN)6 + 2 KOH + H2O2 → 2 K4Fe(CN)6 + 2 H2O + O2
- Hydrogen peroxide (H2O2) reduces ozone (O3) into oxygen (O2).
O3 + H2O2 → H2O + 2 O2
- Hydrogen peroxide bleaches by oxidation. H2O2 bleaches silk, wool, cotton, and hair.
Structure of Hydrogen Peroxide
- The molecular structure of hydrogen peroxide is non-planar and comprises of a pair of oxygen atoms that are linked by a single covalent bond referred to as the peroxide bond.
- The molecular structure of hydrogen peroxide (H2O2) is characterized by an open-book configuration, featuring spins of oxygen atoms bonded together.
- Each oxygen atom is covalently bonded to a single hydrogen atom. The non-bonding electron pairs exhibit repulsion with each other over the oxygen atoms, resulting in the two bonds being positioned in a non-coplanar orientation.
- The dihedral angle between the two planes of gaseous hydrogen peroxide is measured at 111.5o, whereas in its crystalline state, the angle is observed to be 90.2o. This phenomenon is a result of intramolecular hydrogen bonding.
Preparation Of Hydrogen Peroxide by Industrial Methods
There are several methods for preparing hydrogen peroxide.
From 2-ethyl anthraquinone
The flow of hydrogen gas is facilitated through the utilization of 2-ethyl anthraquinone, which is dissolved in benzene and accompanied by a palladium catalyst. The substance in question has undergone a process of decomposition, resulting in the formation of 2-ethyl anthraquinol. Subsequently, a blend comprising 2-ethyl anthraquinol, benzene, and cyclohexanol is subjected to a process of aeration. The production of hydrogen peroxide is facilitated through the process of oxidation, whereby it is converted back to its precursor compound, 2-ethyl anthraquinone.
Electrolysis of Sulphuric Acid
The electrolysis of 30% ice-cold H2SO4 results in hydrogen peroxide. When an acidified sulfate solution is electrolyzed at a high current density, peroxodisulfate (S2O82-) is obtained. It is then hydrolyzed to get H2O2.
2 HSO–4 (aq) [Electrolysis] → HO3SOOSO3H (aq) [Hydrolysis] → 2 HSO–4 (aq)+ 2H +(aq) + H2O2 (aq)
Mechanism Of Reaction
Electrolyte: 30% dilute H2SO4
2 H2SO4 → 2H+ + 2 HSO–4
Cathode: Pb wire
2 H+ + 2e– → H2
Anode: Pt rod
2 HSO–4 → H2S2O8 + 2e– [Peroxide Sulphuric Acid (Marshall’s acid)]
H2S2O8 + H2O → H2SO5 + H2SO4 [Peroxomono Sulphuric Acid (Caro’s acid)]
H2SO5 + H2O → H2SO4 + H2O2
Oxidation of Isopropyl Alcohol
The combination of a small quantity of hydrogen peroxide with isopropyl alcohol functions as an initiator. At approximately 340 Kelvin, and under slight pressure, oxygen is diffused across the solution. The oxidation reaction yields acetone and hydrogen peroxide as its products.
CH3CHOHCH3 (Isopropyl alcohol)+O2 → CH3COCH3 (Acetone) + H2O2
Preparation Of Hydrogen Peroxide by Laboratory Method
Merk’s Process [From Sodium Peroxide]
The process involves the gradual addition of sodium peroxide to a 20% solution of sulphuric acid that is maintained at a low temperature by surrounding it with ice and continuously agitating it. Upon further cooling of the solution, Na2SO4.10H2O crystals precipitate and can be separated via filtration. The solution is an aqueous solution of 30% H2O2.
From Barium Peroxide
A paste of hydrated barium peroxide (BaO2.8H2O) prepared in water at low temperature is subjected to treatment with a 20% solution of sulphuric acid at low temperature. The process of filtration is employed for the purpose of eliminating the white-colored BaSO4 precipitate. The solution retains approximately 5% of hydrogen peroxide.
BaO2⋅8H2O + H2SO4 → BaSO4 (White ppt) + H2O2 + 8H2O
Limitations: The inefficiency of this method can be attributed to the formation of a protective coating around H2O2 by barium sulfate, which hinders the progress of the chemical reaction. The Ba2+ ions present in the solution exhibit a gradual catalytic decomposition of hydrogen peroxide. Consequently, the solution is not amenable to long-term storage. Phosphoric acid is the preferred substance for conducting the test, as opposed to sulphuric acid. The complete precipitation of barium phosphate occurs, thereby eliminating the possibility of H2O2 degradation in the absence of Ba2+ ions.
3BaO2⋅8H2O + 2H3PO4 → Ba3(PO4)2 (ppt) + 24H2O + 3H2O2
The action of Carbon-dioxide
The production of H2O2 and BaCO3 can be achieved by bubbling a swift stream of CO2 through a slim paste of BaO2 in ice cold water. The process involves the separation of insoluble barium carbonate through filtration, resulting in the production of a diluted solution of hydrogen peroxide.
BaO2 + H2O + CO2 → BaCO3 + H2O2
By the action of Phosphoric Acid
Hydrogen peroxide may be synthesized through the reaction of phosphoric acid with barium peroxide. The majority of heavy metal impurities found in BaO2, which act as catalysts for the decomposition of hydrogen peroxide, are eliminated as insoluble phosphates. Consequently, the resultant H2O2 solution exhibits favorable preservation characteristics.
3 BaO2 + 2 H3PO4 → Ba3(PO4)2 + 3 H2O2
Uses of Hydrogen Peroxide
Hydrogen peroxide is commonly utilized for the purpose of bleaching hair, skin, and teeth owing to its oxidizing bleach properties that enable it to disrupt the chemical bonds of a chromophore. The chromophore is the constituent of a molecule that is accountable for its hue. This alteration leads to the formation of a distinct substance that either lacks a chromophore or comprises a chromophore that is incapable of assimilating visible light. In various laboratory investigations, it has been demonstrated that H2O2 has the potential to cause harm to skin cells through a mechanism referred to as oxidative stress.
- The popularity of hydrogen peroxide in pulp bleaching processes is increasing because of the shift from chlorinated bleaches to eco-friendly bleach alternatives. H2O2 finds its application in three key areas of the pulp and paper industry. These include cellulose bleaching, pulp bleaching, and waste paper recycling, where it is used to eliminate ink and color from the paper.
- Municipal water systems have been using hydrogen peroxide as a chemical treatment for many years. The benefits of it include the removal of iron and hydrogen sulfide, as well as the neutralization of tastes and odors.
- The usage of this product in the textile sector is decreasing. H2O2 is commonly used in full bleaching to oxidize reductive dyes before dyeing. Hydrogen peroxide consumption for bleaching is increasing due to its environmentally friendly nature as a substitute for chlorine-based bleaches.
- Hydrogen peroxide is a topical agent that exhibits antiseptic, antibacterial, antifungal, and antiviral properties.
- Hydrogen peroxide is utilized for the purpose of sanitizing the area of application and as a preventive measure against subsequent infections of the exposed laceration, abrasion, or incision.
- H2O2 exhibits antimicrobial properties due to its ability to eliminate bacteria and fungi.
- H2O2 exhibits antibacterial, antiviral, antifungal, antifungal, and sporicidal properties.
The mechanism of action of hydrogen peroxide involves the release of oxygen upon topical application to the affected site. The oxygen that is released creates a frothy and foamy substance that aids in the cleansing of the designated area. Hydrogen peroxide exhibits emulsifying properties that enhance its surface activity, thereby mitigating pruritus, erythema, inflammation, and irritation of the integument. Hydrogen peroxide is utilized for the treatment of superficial infections, skin breaks, pressure sores, leg sores, and surface-level itches
- Hydrogen peroxide can be utilized to sanitize the interior of household appliances such as refrigerators and dishwashers. Due to its non-toxic nature, it presents itself as a favorable alternative for the purpose of cleaning appliances that are utilized for food preservation or for cleaning dishes and utensils.
- Hydrogen peroxide can be utilized to sterilize a soiled sponge. Prepare a solution by mixing equal quantities of hydrogen peroxide and warm water in a shallow container. Submerge the sponge(s) in the solution for approximately 10 minutes. It is recommended to thoroughly rinse the sponges and subsequently allow them to air dry.
- One effective method for removing stubborn residues from cookware involves creating a mixture of baking soda and hydrogen peroxide to form a paste. Apply a substantial amount of the paste onto the affected area, and allow it to remain undisturbed for a period of time. After a period of time, return to the surface and thoroughly clean it, resulting in the removal of any stubborn, baked-on stains.
- To ensure proper hygiene, it is recommended to cleanse and disinfect the cutting board and countertop by applying peroxide through spraying or wetting. Allow the solution to effervesce for a brief period, subsequently utilize a scrubbing motion to cleanse the surface, and conclude by rinsing thoroughly.
- Ensure proper hygiene of your toilet bowl by thoroughly cleaning and sanitizing it to achieve a pristine and spotless appearance. Add 1/2 cup of hydrogen peroxide to the toilet bowl, allow it to remain for a duration of 20 minutes, and subsequently, utilize a toilet brush to scrub the bowl clean.
- Hydrogen peroxide can be used as a pretreatment agent to eliminate stains from various fabrics such as clothing, curtains, and tablecloths. Allow the stain to remain on the fabric for a brief period before placing it into the washing machine.
- Incorporating one cup of hydrogen peroxide into a standard load of white garments can serve as a viable substitute for bleach, effectively enhancing the brightness and whiteness of the fabrics.
Hydrogen Peroxide for Plants
- Plant enthusiasts and cultivators utilize Oxygen Plus Hydrogen Peroxide 3% or 6% double-strength to prevent and remedy various plant ailments, as well as to enhance plant health and reestablish a more favorable equilibrium for optimal indoor plant growth.
- H202 has been found to exhibit bactericidal and fungicidal properties in soil, thereby eliminating the microorganisms that cause root rot.
- Additionally, it facilitates the restoration of oxygen levels in the soil, which aids in the expedited recovery of the surviving roots. The prescribed method entails the use of a 1:1 proportion of Oxygen Plus 3% and water. In order to ensure complete saturation of the potting mix, it is recommended to water from either the bottom or the top. It is advisable to refrain from pouring liquid onto leaves as it may cause them to experience a burning sensation.
- The provision of additional oxygen to roots is facilitated by H2O2, thereby promoting growth and germination.
- In hydroponic gardens, the proliferation of detrimental bacteria is facilitated by water with insufficient oxygen levels. Hydrogen peroxide (H2O2) at a concentration of 3% is utilized in hydroponic systems to enhance oxygen levels and counteract the occurrence of low oxygen levels in warm, ambient temperature water.
- To provide adequate hydration to the plant, it is recommended to irrigate it with a solution consisting of four cups of water and a quarter cup of hydrogen peroxide with a concentration of 3%. Completely saturate the soil by watering it until the mixture begins to drip out of the drainage holes. It is recommended to tilt the pot while potting to ensure even coverage of the potting mix.
Frequently Asked Question (FAQ)
Is Hydrogen Peroxide Safe?
Hydrogen peroxide is a compound with the molecular formula H2O2, which exhibits chemical properties. Ingestion of the substance may result in severe adverse reactions. Keep it locked up in a cupboard where kids and animals can’t get to it.
Does hydrogen peroxide whiten teeth?
The utilization of hydrogen peroxide in the form of a rinse or a paste has been observed to potentially facilitate the process of teeth whitening. However, an elevated concentration has the potential to induce adverse effects, such as detrimental impacts on your dental health.
Does Hydrogen peroxide expires?
Under standard conditions, a hydrogen peroxide solution with a concentration of 3% and stored at room temperature is anticipated to undergo a decay of 0.5% annually. Upon opening the seal, it is advisable to utilize the peroxide solution expeditiously due to its susceptibility to accelerated degradation into water upon exposure to air. Similarly, in the event of bottle contamination, such as through swab or finger contact, it is reasonable to anticipate a reduction in the efficacy of the remaining solution.
In the event that a bottle of hydrogen peroxide has been stored in a medicine cabinet for an extended period of time, particularly if the container has been opened, it is advisable to presume that the substance has undergone partial or complete degradation, thereby rendering it ineffective as a disinfectant.
Prior to utilizing H2O2, it is advisable to verify the expiration date. It is advisable to store peroxide in its native brown container or a dimly lit spray bottle to prevent photochemical reactions caused by light exposure. In the event that the solution no longer exhibits a foaming reaction, it is recommended to dispose of it via the sink and procure a fresh container.
Video on Hydrogen Peroxide