Which of the following is the strongest acid?

• A. ClO₃(OH)
• B. ClO₂(OH)
• C. SO(OH)₂
• D. SO₂(OH)₂

To determine which of the given compounds is the strongest acid, we need to analyze their structures and the stability of their conjugate bases. The compounds listed are all oxyacids, which means they contain oxygen, hydrogen, and another element (in this case, chlorine or sulfur). The strength of an acid is often related to how easily it can donate a proton (H⁺) and how stable the resulting conjugate base is after the proton is lost.

Understanding Oxyacids

Oxyacids are acids that contain oxygen, and their strength can be influenced by several factors, including the electronegativity of the central atom and the number of oxygen atoms bonded to it. Generally, the more electronegative the central atom and the more oxygen atoms present, the stronger the acid tends to be. This is because additional oxygen atoms can stabilize the negative charge on the conjugate base through resonance.

Analyzing the Compounds

• ClO₃(OH): This compound has chlorine as the central atom with three oxygen atoms. The presence of multiple oxygen atoms suggests a strong acid due to resonance stabilization of the conjugate base.
• ClO₂(OH): Here, chlorine is bonded to two oxygen atoms. While it is still an oxyacid, it has less resonance stabilization compared to ClO₃(OH).
• SO(OH)₂: In this case, sulfur is the central atom with two hydroxyl groups. Sulfur can form strong acids, but the presence of only two oxygen atoms limits its strength compared to those with more oxygen.
• SO₂(OH)₂: This compound has sulfur bonded to four oxygen atoms (two hydroxyl groups and two double-bonded oxygen atoms). The increased number of oxygen atoms enhances the acid's strength due to better resonance stabilization of the conjugate base.

Comparative Strength

When comparing these acids, we can summarize their potential strengths based on the number of oxygen atoms and the central atom's electronegativity:

• ClO₃(OH) has three oxygen atoms, which provides good resonance stabilization.
• ClO₂(OH) has only two oxygen atoms, making it weaker than ClO₃(OH).
• SO(OH)₂ has two hydroxyl groups but fewer oxygen atoms overall compared to the others.
• SO₂(OH)₂ has four oxygen atoms, which significantly enhances its ability to stabilize the conjugate base.

Conclusion on Acid Strength

Given this analysis, the strongest acid among the options is SO₂(OH)₂. Its structure allows for the greatest resonance stabilization of the conjugate base, making it more effective at donating protons compared to the other compounds listed. Thus, when considering the factors that influence acid strength, SO₂(OH)₂ stands out as the most potent acid in this group.