Question

Which species, \(\mathrm{H}_{2} \mathrm{~S}\) or HS \(^{-}\), ionizes to the greater extent in water? Explain.

Short answer

The species that ionizes to a greater extent in water is the Hydrogen sulfide anion (HS\(^{-}\)).

Step-by-step solution

Understanding Hydrogen Sulfide (\(H_{2}S\)) in Water

Hydrogen sulfide is a non-polar molecule that does not readily ionize in water because of the lack of polarity in the \(H-S\) bond. The overlap of hydrogen's \(1s\) orbital with sulfur's \(3p\) orbital results in covalent bonding and a molecule with little tendancy to ionize.

Understanding Hydrogen Sulfide Anion (HS\(^{-}\)) in Water

The hydrogen sulfide anion, HS\(^{-}\), on the other hand, is capable of ionizing to a much higher extent partially due to its extra electron. The HS\(^{-}\) is a polar molecule, and in the presence of water, it can donate its extra electron to form hydroxide ions (\(OH^{-}\)). Thus, this species is more likely to ionize in water.

Comparing the Extent of Ionization

After examining the behavior of both species in water, we can conclude that the species that ionizes to the greater extent in water is the hydrogen sulfide anion HS\(^{-}\). This is due to the polarity of HS\(^{-}\) and the ability to form \(OH^{-}\) ions in water.

Key concepts

hydrogen sulfide

Hydrogen sulfide, known by its chemical formula \(H_2S\), is a colorless gas often recognized by its distinct rotten egg smell. It is composed of two hydrogen atoms covalently bonded to a sulfur atom. This compound belongs to a class of molecules known as non-polar molecules. Non-polar molecules have an even distribution of electrical charge across the molecule.
\(H_2S\) doesn't readily ionize in water due to the non-polar nature of the \(H-S\) bonds. This means that the bonds do not favor breaking apart into charged ions in an aqueous environment.
Instead, the hydrogen and sulfur atoms share electrons through covalent bonds, with the hydrogen's 1s orbital overlapping with sulfur's 3p orbital. This overlap creates a stable connection that is not naturally inclined to dissolve into ions when in contact with water.

polarity

Polarity is a key concept in chemistry referring to the distribution of electric charge across a molecule. When discussing molecules like \(H_2S\) and its anion \(HS^-\), polarity plays a significant role in their behavior in water.
The anion \(HS^-\) is polar, which is in contrast to its neutral counterpart \(H_2S\). This polarity in \(HS^-\) arises because of its uneven distribution of electrons, resulting from gaining an extra electron to form the anion. The extra electron presence enhances the overall dipole moment of the molecule.
When polar molecules like \(HS^-\) are introduced into water, they can interact with water's polar nature. This interaction facilitates ionization, aiding in the ability of \(HS^-\) to donate its extra electron and form \(OH^-\) ions, thus making it more reactive in the aqueous phase compared to non-polar \(H_2S\).

• Polar molecules have regions of partial positive and negative charges.
• They can dissolve and interact more readily in polar solvents like water.
• Polarity affects the molecule's solubility and reactivity in different environments.

covalent bonding

Covalent bonding involves the sharing of electron pairs between atoms, allowing them to adhere and form stable molecules. In \(H_2S\), covalent bonds form when the hydrogen atoms share their electrons with the sulfur atom.
This type of bond is pivotal in maintaining the structure of \(H_2S\) as a molecule, and it results from the overlap of atomic orbitals. Specifically, the hydrogen's 1s orbital merges with the sulfur's 3p orbitals, leading to the shared electron cloud that constitutes the covalent bond.
Unlike ionic bonds, where electrons are transferred completely from one atom to another, covalent bonds often involve atoms with similar electronegativities. This similarity helps the bonded atoms attain a more stable electron configuration.

• Covalent bonds form when atoms share electrons evenly to achieve stability.
• These bonds make molecules such as \(H_2S\) less likely to ionize in non-polar environments.
• The strong electron sharing in \(H_2S\) results in a non-polar structure, influencing its chemical behavior significantly.