ACS Chemistry Practice Exam 2026 – The All-in-One Guide to Exam Success!

The general solubility rule for sulfates (SO4 2-) states that most sulfates are soluble in water, with certain exceptions. The correct choice highlights that sulfates are soluble except in the presence of specific cations such as strontium (Sr2+), mercury (Hg2+), barium (Ba2+), lead (Pb2+), and calcium (Ca2+).

These exceptions arise because these particular cations form sulfates that are significantly less soluble in water due to their relatively higher lattice energies compared to the solvation energy gained when they dissolve. For instance, the sulfate salts of barium and lead are known to precipitate out of solution due to this decreased solubility. This makes option B an accurate reflection of the solubility behavior of sulfates in relation to specific ions.

In contrast, sulfates are generally considered soluble when combined with alkali metals (like sodium and potassium) and with ammonium (NH4+), establishing the broader pattern of solubility that option B encompasses.