Which is the weakest acid from the following?

• A. H₂S
• B. H₂Se
• C. H₂Te
• D. All would have the same acid strength.

Answer: (A)

Verified step by step guidance

1. Understand that acid strength generally increases with the size of the central atom in the molecule. Larger atoms tend to form weaker bonds with hydrogen, making it easier for the molecule to donate a proton.
2. Consider the periodic table position of the central atoms in the acids: sulfur (S), selenium (Se), and tellurium (Te). These elements are in the same group (Group 16) and their atomic size increases as you move down the group.
3. Recognize that H2S, H2Se, and H2Te are all hydrides of Group 16 elements. As you move down the group, the bond strength between hydrogen and the central atom decreases, which typically results in stronger acids.
4. Compare the bond strengths: H-S, H-Se, and H-Te. The H-S bond is stronger than the H-Se and H-Te bonds, meaning H2S is less likely to donate a proton compared to H2Se and H2Te.
5. Conclude that H2S is the weakest acid among the given options because it has the strongest bond with hydrogen, making it less likely to dissociate and donate a proton.