Question

Account for each of the following observations: (a) \(\mathrm{H}_{2} \mathrm{SO}_{4}\) is a stronger acid than \(\mathrm{H}_{2} \mathrm{SO}_{3}\) (b) \(\mathrm{SF}_{4}\) exists, but \(\mathrm{OF}_{4}\) does not. (c) The \(\mathrm{S}_{8}\) ring is nonplanar.

Short answer

(a) Sulfuric acid is stronger due to resonance stabilization. (b) \(\mathrm{SF}_4\) can form due to sulfur's ability to expand its octet; \(\mathrm{OF}_4\) cannot as oxygen can't. (c) \(\mathrm{S}_8\) is nonplanar to minimize strain.

Step-by-step solution

Compare Acid Strengths

Sulfuric acid (\(\mathrm{H}_2\mathrm{SO}_4\)) and sulfurous acid (\(\mathrm{H}_2\mathrm{SO}_3\)) differ in their chemical structure. \(\mathrm{H}_2\mathrm{SO}_4\) contains two sulfate (SO_4^2-) ions, providing it with a better capability to stabilize additional negative charges by resonance, thus making it a stronger acid compared to \(\mathrm{H}_2\mathrm{SO}_3\). Also, \(\mathrm{H}_2\mathrm{SO}_4\) has more oxygens bound to sulfur, allowing for better delocalization of charge, leading to increased acidity.

Examine the Existence of Compunds

\(\mathrm{SF}_4\) exists because sulfur can expand its octet, accommodating more than eight electrons around it, which allows it to form stable compounds with expanded valence shells like \(\mathrm{SF}_4\). However, oxygen cannot expand its octet due to its inability to accommodate more than eight electrons effectively, hence \(\mathrm{OF}_4\) does not exist.

Analyze the Structure of Sulfur Ring

The \(\mathrm{S}_8\) molecule forms a crown or puckered ring structure, not a planar one. This is because sulfur prefers to form \(\sigma\)-bond networks that minimize strain by adopting nonplanar configurations (i.e., bent or puckered), due to steric and bond angle considerations that favor such geometries.

Key concepts

Chemical Structure

The chemical structure of a molecule greatly influences its properties, including acidity. Acids like \\( \mathrm{H}_2\mathrm{SO}_4 \) and \\( \mathrm{H}_2\mathrm{SO}_3 \) serve as a prime example. The difference in the chemical structure between sulfuric acid and sulfurous acid results in a variance in acid strength. Sulfuric acid, \\( \mathrm{H}_2\mathrm{SO}_4 \), contains one more oxygen atom bonded to sulfur compared to sulfurous acid, \\( \mathrm{H}_2\mathrm{SO}_3 \). This additional oxygen allows for more extensive resonance and better stabilization of negative charges. \

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• The resonance occurs because the sulfate ion (\( \mathrm{SO}_4^{2-} \)) in sulfuric acid can delocalize the charge over more oxygen atoms.
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• This delocalization enhances the molecule’s ability to handle extra negative charges, contributing to higher acidity.

\Therefore, the structural difference directly impacts the strength of these acids, with more oxygens equating to stronger acid properties.

Sulfur Compounds

Sulfur’s ability to expand its valence shell provides it the flexibility to form a variety of compounds. In the case of \\( \mathrm{SF}_4 \), sulfur can expand its octet, meaning it can hold more than eight electrons, forming stable compounds. \This expanded valency is a key characteristic of sulfur, unlike oxygen which is more rigid due to its inability to expand beyond an octet configuration. \

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• \( \mathrm{SF}_4 \) is stable because sulfur can accommodate more electrons in its outer shell, thus forming additional bonds.
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• In contrast, oxygen, with a strict octet rule adherence, cannot form an equivalent \\( \mathrm{OF}_4 \) compound.

\This illustrates how chemical elements within the same group can exhibit different chemistry based on their electronic configurations, particularly their ability to expand their valence shells.

Nonplanar Molecular Structure

The \\( \mathrm{S}_8 \) molecule is a classic example of a nonplanar molecular structure. Rather than forming a flat circle or ring, the \\( \mathrm{S}_8 \) sulfur atoms prefer a crown-shaped formation. This nonplanar structure is influenced largely by the need to minimize strain associated with sterics and bond angles. \

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• The \\( \mathrm{S}_8 \) ring is structured to reduce angle strain, which would be present in a planar form, where bond angles could be less optimal.
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• Sulfur bonds in such rings prefer adopting \\( \sigma \)-networks that prevent unnecessary strain by being nonplanar.
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\Such geometrical preferences are typical in larger and complex structures, and highlight the importance of spatial arrangement in the stability of molecular structures.