Question

Describe the structure and bonding in sulfuric acid, \(\mathrm{H}_{2} \mathrm{SO}_{4}\), and in its two ions, \(\mathrm{HSO}_{4}{ }^{-}\)and \(\mathrm{SO}_{4}{ }^{2-}\).

Short answer

Sulfuric acid has a molecule structure with sulfur atom in the center forming four bonds - two double bonds with oxygen atoms and two single bonds with hydroxyl groups. When it forms the HSO4- ion, one hydrogen atom detaches, leaving a negative charge on one of the oxygen atoms. In the SO42- ion, both hydrogen atoms detach, leaving two negative charges distributed amongst the oxygen atoms.

Step-by-step solution

Structure and Bonding in Sulfuric Acid (H2SO4)

Sulfuric acid has the chemical formula H2SO4. In H2SO4, sulfur (S) is the central atom which is surrounded by four oxygen (O) atoms and two hydrogen (H) atoms. The sulfur atom forms two single bonds with two hydrogen atoms and two double bonds with two oxygen atoms, remaining another two oxygen atoms form single bonds with hydrogen. The two oxygen atoms bonded with sulfur by a double bond are in one plane, making an angle of 120°. This is due to sp2 hybridization of sulfur.

Ionization of Sulfuric Acid and Structure of HSO4- Ion

Sulfuric acid is a dibasic acid. It can lose one proton (H+) to form the hydrogen sulphate ion (HSO4-) and can lose two protons to form the sulphate ion (SO42-). In the HSO4- ion, the sulfur atom is the central atom and is surrounded by four oxygen atoms and one hydrogen atom. One oxygen atom forms a single bond with the hydrogen atom, two oxygen atoms are bonded to sulfur by a double bond and one oxygen atom is bonded to sulfur by a single bond negative charge, which is due to the presence of an extra electron after the loss of one proton.

Structure of SO42- Ion

The SO42- ion is formed when sulfuric acid loses two protons. In the SO42- ion, sulfur is the central atom, surrounded by four oxygen atoms. Each oxygen atom is bonded to the sulfur atom by a double bond. The ion carries a net charge of -2, due to the presence of two extra electrons after the loss of two protons. This molecule is a symmetrical tetrahedral shape.

Key concepts

H2SO4 structure

The chemical structure of sulfuric acid, denoted as \(\text{H}_2\text{SO}_4\), is intriguing due to the geometric arrangement of its atoms. In this compound, sulfur (S) acts as the central atom. It is surrounded by four oxygen (O) atoms and bonded to two hydrogen (H) atoms. The sulfur atom forms two single bonds with the hydrogen atoms, and it connects with two oxygen atoms via double bonds. The remaining two oxygens form single bonds to hydrogen atoms.
The unique layout of sulfuric acid results in its distinctive molecular geometry. The oxygen atoms that form double bonds with sulfur align in a plane with a bond angle of 120 degrees. This specific angle is a result of the sp2 hybridization of the sulfur atom, creating a plane where these oxygen atoms reside.

acid ionization

Sulfuric acid is known as a dibasic acid, meaning it can donate two protons (H+ ions). This ionization occurs in two distinct steps, producing two types of ions. Initially, \(\text{H}_2\text{SO}_4\) ionizes to lose one proton, resulting in the hydrogen sulfate ion \(\text{HSO}_4^-\).
Further ionization occurs when \(\text{HSO}_4^-\) loses another proton, forming the sulfate ion \(\text{SO}_4^{2-}\). This complete donation of two protons is what characterizes sulfuric acid's strong acidic nature. Understanding this ionization process is critical to grasping the behavior of sulfuric acid in chemical reactions.

chemical bonding

In sulfuric acid and its ions, chemical bonding is responsible for the stability and properties of the molecules. The key type of bonds in \(\text{H}_2\text{SO}_4\) are covalent bonds. Sulfur forms double covalent bonds with two oxygen atoms, which involves sharing two pairs of electrons between sulfur and oxygen.
The other oxygen atoms are involved in hydrogen bonding, forming single covalent bonds with the hydrogen atoms. In the ions formed through ionization, the presence of extra electrons on the oxygen creates negative charges, stabilizing the ions. These bond interactions highlight the intricate nature of chemical bonding within and beyond sulfuric acid.

sp2 hybridization

Sulfur in \(\text{H}_2\text{SO}_4\) undergoes \(sp^2\) hybridization to accommodate its bonding needs with oxygen atoms. Hybridization is a concept where atomic orbitals mix to form new hybrid orbitals suitable for bond formation. In sulfuric acid, the \(sp^2\) hybridization helps sulfur promote one \(3p\) electron to the otherwise unoccupied \(3d\) subshell. This results in three \(sp^2\) hybrid orbitals and one pure \(p\) orbital available for forming bonds.
The \(sp^2\) hybridization accounts for the 120-degree bond angle observed in the plane of the double-bonded oxygen atoms. This hybridization helps explain the molecular geometry and electronic distribution that is crucial for understanding the reactivity and properties of sulfuric acid.