Which of the following ions is generally soluble, with exceptions such as Ba, Hg, and Pb?

Sulfate ions (SO₄²⁻) are generally soluble in water due to their ability to interact favorably with water molecules. Most sulfate salts are soluble, making them important in various chemical reactions and processes. However, there are notable exceptions where certain cations lead to insoluble sulfate compounds. Barium sulfate (BaSO₄), mercury(II) sulfate (HgSO₄), and lead(II) sulfate (PbSO₄) are examples of sulfates that do not dissolve well in water, highlighting the influence of specific metal ions on solubility.

The other options, such as oxalate, thiosulfate, and phosphate, have different solubility behaviors. Oxalate ions (C₂O₄²⁻) typically form insoluble compounds with many metal ions. Thiosulfate ions (S₂O₃²⁻) can vary in solubility, but many salts containing thiosulfate are not as universally soluble as sulfates. Phosphate ions (PO₄³⁻) commonly form insoluble salts with a variety of cations, making them generally less soluble compared to sulfates. Thus, the distinctive solubility characteristics of