Hydrogen Peroxide(H2O2) Properties (25 Facts You Should Know)

Hydrogen peroxide is an unstable compound that decomposes in presence of light and heat. Let us explore the physical and chemical properties of hydrogen peroxide.

Hydrogen peroxide is a reactive oxygen species and becomes miscible in water. It is also soluble in ether. It is stored in a dark bottle (to get rid of light) with a stabilizer in a weakly acidic solution. The mixture of hydrogen peroxide and water behaves as a eutectic mixture showing a freezing point below 56⁰ C.

Let us focus on the IUPAC name, reactions, polarity, magnetic behavior, melting, and boiling point of H₂O₂ briefly in this article.

Hydrogen Peroxide IUPAC Name

The IUPAC (International Union of Pure and Applied Chemistry) name of hydrogen peroxide is hydrogen peroxide itself.

Hydrogen Peroxide Chemical Formula

Hydrogen peroxide has the chemical formula H₂O₂.

Hydrogen Peroxide CAS Number

H₂O₂ has the CAS registry number 7722-84-1.

Hydrogen Peroxide Chem Spider ID

H₂O₂ has the ChemSpider (ChemSpider is a free chemical structure database) ID 763.

Hydrogen Peroxide Chemical Classification

• H₂O₂ can be chemically classified as an inorganic liquid compound.
• H₂O₂ can be chemically classified as a weakly acidic compound.
• H₂O₂ can be chemically classified as a covalent compound.
• H₂O₂ can be chemically classified as a reactive oxygen species and catalase.

Hydrogen Peroxide Molar Mass

The molar mass of H₂O₂ is 34.0147 g. This value of the molar mass is obtained from the summation of the molar mass of 2 oxygen atoms and 2 hydrogen atoms which are 15.999 g/mole (molar mass of one oxygen atom) and 1.00784 g/mole (molar mass of 1 H atom) respectively.

Hydrogen Peroxide Color

Pure H₂O₂ is pale blue. But it appears as a colorless liquid.

Hydrogen Peroxide Viscosity

H₂O₂ has a viscosity of 1.245 centipoises at 20⁰ F and 1 atm. It has a slightly higher viscosity than water (the viscosity of water is 1 centipoise).

Hydrogen Peroxide Molar Density

The molar density of H₂O₂ is 0.0326 mol/cm³ because it has a density of 1.11 g/cm³ (20⁰ C, 30% w/w solution) and a molar mass of 34.0147 g/mol.

Hydrogen Peroxide Melting Point

H₂O₂ has a melting point of -0.43⁰ C or -31.23⁰ F.

Hydrogen Peroxide Boiling Point

The boiling point of H₂O₂ is 150.2⁰ C or 302.4⁰ F.

Hydrogen Peroxide state at Room Temperature

At room temperature, H₂O₂ appears as a colorless liquid compound because there is a strong intermolecular hydrogen bonding present between the H₂O₂ molecules.

Hydrogen Peroxide Ionic/Covalent Bond

H₂O₂ is a covalent molecule. There are three covalent bonds present in the structure of H₂O₂. There is also one O-O bond and two O-H bonds having the length of 147.4 pm and 95.0 pm respectively present in H₂O₂ and the dihedral angle of this compound is 111⁰.

Hydrogen Peroxide Electron Configurations

Electron configuration defines the distribution of the electrons in different energy levels, known as electronic orbitals. Let us see the electron configuration of H₂O₂ in detail.

H₂O₂ has the electron configuration of [He] 2s² 2p⁴ for oxygen and 1s¹ for hydrogen atom.

Hydrogen Peroxide Oxidation State

The oxidation state of H₂O₂ is 0 because it is a neutral compound. 2 oxygen atoms are in O₂^2- and each of the 2 hydrogen atoms is in a +1 (H⁺) oxidation state.

Hydrogen Peroxide Acidity/Alkaline

H₂O₂ is an acidic liquid compound that forms hydroperoxide and peroxide salts. It is a weak acid with an acid dissociation constant (K_a) of 10^-11.6 or pk_a = 11.6. H₂O₂ = 2H⁺ + O₂^2-.

Is Hydrogen Peroxide odorless?

H₂O₂ is not an odorless compound and has a slightly sharp odor at low concentrations.

Is Hydrogen Peroxide paramagnetic?

Paramagnetism arises due to the presence of unpaired electrons which are attracted by the weak magnetic field. Let us check the magnetism of H₂O₂.

H₂O₂ is not a paramagnetic compound because there are no unpaired electrons present in H₂O₂. It is diamagnetic because each of the two oxygen atoms is sp³ hybridized and all the electrons of oxygen as well as the two hydrogen atoms are paired up in those four sp³ hybrid orbitals.

Hydrogen Peroxide Hydrates

H₂O₂ can form intermolecular hydrogen bonding with other H₂O₂ molecules. It acts as both the hydrogen bond donor and acceptor and appears as a liquid substance. It accepts hydrogen bonds through its two oxygen and donates through hydrogen atoms.

Hydrogen Peroxide Crystal Structure

The colorless crystal of H₂O₂ has a tetragonal structure with the space group of D₄⁴ -P4₁2₁. There are four molecules per unit cell. The lattice parameters a and c are 4.06 A⁰ and 8.00 A⁰.

Hydrogen peroxide Polarity and Conductivity

• H₂O₂ is a polar molecule with a dipole moment of 2.26 D. This polarity arises due to the presence of the two polar O-H bonds. The bond moment of the two O-H bonds cannot be canceled by each other due to having a bent shape and a 109⁰-111⁰ dihedral angle.
• H₂O₂ is a very weak electrolyte with low electrical conductivity power. It has a specific conductance value of 1.5×10^-6. It also acts as a very good ionizing solvent.

Hydrogen Peroxide Reaction with Acid

H₂O₂ reacts with acetic acid (CH₃COOH) and hydrochloric acid (HCl) to form peracetic acid and hypochlorous acid respectively.

• CH₃COOH + H₂O₂ = CH₃COOOH + H₂O
• HCl + H₂O₂ = HOCl + H₂O

Hydrogen Peroxide Reaction with Base

H₂O₂ reacts with the strong base, sodium hydroxide (NaOH) and forms sodium peroxide and water.

NaOH + H₂O₂ = Na₂O₂ + H₂O

Hydrogen Peroxide Reaction with Metal

• H₂O₂ undergoes a decomposition reaction in presence of finely divided metals to liberate gaseous oxygen.
• 2H₂O₂ + Metal = 2H₂O + O₂.
• Iron and H₂O₂ can oxidize a wide range of substrates. This reaction is known as the Fenton reaction.
• Fe²⁺ + H₂O₂ + = Fe³⁺ + OH˙ (hydroxyl radical) + OH^– (hydroxyl ion).

Hydrogen Peroxide Reaction with Oxide

H₂O₂ reacts with silver oxide and manganese dioxide and liberates oxygen.

• H₂O₂ + Ag₂O = 2Ag + O₂ +H₂O
• H₂O₂ + MnO₂ +2H⁺ = Mn²⁺ + O₂ + 2H₂O

Conclusion

Hydrogen peroxide is used as a good oxidizing agent, bleaching agent, and antiseptic (dilute solution of H₂O₂) also. It is a very unstable intermediate formed in the human body that can cause the oxidation of protein, lipid membrane, and DNA due to the formation of peroxide ions.