Hydrogen Sulfide(H2S) Properties (25 Facts You Should Know)

Hydrogen sulfide is a chalcogen colorless and hydride gas. Let us discuss the physical and chemical properties of hydrogen sulfide.

Hydrogen sulfide is an inflammable gas that exists in the air atmosphere in trace amounts. It is produced from organic substances in absence of oxygen due to the microbial breakdown process. It slowly forms elemental sulfur gas when exposed to air and is slightly soluble in water (3.980 g/litre).

Let us focus on the IUPAC name, radius, magnetism, polarity, reactions, melting, and boiling point of hydrogen sulfide in detail in this article.

H₂S IUPAC Name

The IUPAC (International Union of Pure and Applied Chemistry) name of H₂S is hydrogen sulfide.

H₂S Chemical Formula

Hydrogen sulfide has the chemical formula H₂S.

H₂S CAS Number

H₂S has the CAS registry number (authentic numeric identifier which can contain up to 10 digits) 7783-06-4.

H₂S Chem Spider ID

H₂S has the ChemSpider (ChemSpider is a free chemical structure database) ID 391.

H₂S Chemical Classification

• H₂S can be chemically classified as an inorganic gaseous compound.
• H₂S can be chemically classified as an acidic compound.
• H₂S can be chemically classified as a covalent compound.
• H₂S can be chemically classified as chalcogen hydride gas.

H₂S Molar Mass

The molar mass of H₂S is 34.08 g. This value of the molar mass is obtained from the summation of the molar mass of one sulfur atom and two hydrogen atoms which are 32.065 g/mole and 1.00784 g/mole (molar mass of 1 H atom) respectively.

H₂S Color

H₂S is a colorless, inflammable, and gaseous compound.

H₂S Viscosity

H₂S has a viscosity of 0.01166 centipoises at 32⁰ F and 1 atm.

H₂S Molar Density

The molar density of H₂S is 0.0452 mol/L because it has a density of 1.539 g/L (at 273 K).

H₂S Melting Point

H₂S has a melting point of -85.5⁰ C or -121.9⁰ F.

H₂S Boiling Point

The boiling point of H₂S is -59.55⁰ C or -75.19⁰ F.

H₂S state at Room Temperature

At room temperature, H₂S appears as a colorless gaseous compound because the intermolecular hydrogen bonding in H₂S is relatively weak than H₂O.

H₂S Ionic/Covalent Bond

H₂S is a covalently bonded molecule. There are two covalent bonds present in the structure of H₂S. All of the two S-H bonds are equivalent and they share their valence electron pairs mutually between them and the bonded electron pairs are slightly shifted towards sulfur due to its greater electronegativity.

H₂S Covalent Radius

The ionic radius of the sulfur (S^2-) is 186 pm and the atomic radius of hydrogen is 53 pm.

H₂S Electron Configurations

Electron configuration shows the arrangement of the electrons in different energy states, known as electronic shells. Let us explain the electron configuration of H₂S in detail.

H₂S has the electron configuration [Ne] 3s² 3p⁴ and 1s¹.

H₂S Oxidation State

H₂S is in the oxidation state of 0 because it is a neutral compound. Sulfur is in -2 (S^2-) and each of the two hydrogen atoms is in a +1 (H⁺) oxidation state.

H₂S Acidity/Alkaline

H₂S is an acidic (Bronsted as well as lewis acid) gaseous compound. It is a weak acid with an acid dissociation constant (K_a) of 10^-7 or pk_a = 7. H₂S = 2H⁺ + S^2-.

Is H₂S odorless?

H₂S is not an odorless compound because it has a pungent “rotten egg” odor at low concentrations.

Is H₂S paramagnetic?

The presence or absence of unpaired electrons which are attracted by the weak magnetic field determines the magnetic behavior of a compound. Let us check the magnetism of H₂S.

H₂S is not a paramagnetic but diamagnetic compound because there are no unpaired electrons present in H₂S. Sulfur in H₂S is sp³ hybridized and all the electrons of sulfur as well as the two hydrogen atoms are paired up in those four sp³ hybrid orbitals.

H₂S Hydrates

H₂S forms gas hydrates with water molecules at low temperatures and high pressure. Stable hydrates are formed when H₂S gas molecules are trapped in the cage-like structure developed by the water molecules.

H₂S Crystal Structure

The colorless crystal of H₂S has a structure of fluorite with the space group of cubic Fm3m and point group C_2v. In the crystal, each H⁺ is bonded with four S^2- to form a mixture of corner and edge-sharing HS₄ tetrahedra. The lattice parameters are a= b= c = 4.59 A⁰, and α = β = γ = 90⁰.

H₂S Polarity and Conductivity

• Hydrogen sulfide is a polar molecule with a dipole moment of 0.97 Debye. This chemical polarity of H₂S arises because of its bent shape. Due to having this shape the bond dipole of two S-H bonds cannot be canceled out by each other.
• H₂S is a metallic conductor of electricity above 90 GPa (gigapascal). When it is cooled down below its critical temperature, it exhibits superconductivity.

H₂S Reaction with Acid

Though H₂S is weakly acidic, it reacts with strong sulfuric acid (H₂SO₄) and forms elemental sulfur, sulfur dioxide (SO₂), and H₂O.

H₂S + H₂SO₄ = S + SO₂ + 2H₂O

H₂S Reaction with Base

H₂S reacts with a strong base, sodium hydroxide (NaOH) in two manners, and two different products are also obtained.

• H₂S + NaOH (excess) = NaS (sodium sulfide) + H₂O.
• H₂S (excess) + NaOH = NaHS (sodium bisulfide) + H₂O.

H₂S Reaction with Oxide

H₂S undergoes a redox reaction with an oxygen molecule and forms elemental sulfur with water. In this reaction, H₂S is oxidized and oxygen is reduced.

2H₂S + O₂ = 2S + 2H₂O

H₂S Reaction with Metal

H₂S reacts with different metal ions and forms the precipitate of metal sulfide.

• Cu²⁺ + H₂S = CuS (ppt) + 2H⁺
• Hg²⁺ + H₂S = HgS (ppt) + 2H⁺
• Pb²⁺ + H₂S = PbS (ppt) + 2H⁺
• 2Sb³⁺ + 3H₂S = Sb₂S₃ (ppt) + 6H⁺

Conclusion

Though hydrogen sulfide is not good for animal health it is used to produce sulfuric acid (H₂SO₄) and elemental sulfur (S), inorganic sulfides, etc. These sulfides are applied in the leather, pharmaceutical, and pesticide industry. It is also used to form heavy water (D₂O) for nuclear power plants.