Sulfate salts are generally soluble. Which of these sulfates is an exception and therefore insoluble?

1. The sulfate ion normally gives soluble salts. 2. The listed exceptions are the sulfates of Ag+, Ba2+, Ca2+, Hg2 2+, Pb2+ and Sr2+. 3. Barium sulfate is on that list, so it is insoluble and precipitates. 4. Potassium, sodium and ammonium are group 1 or ammonium cations, whose salts carry no exceptions. 5. So mixing potassium sulfate with barium nitrate throws down BaSO4. _Source: OpenStax Chemistry (CC BY 4.0), Ch 4 "Stoichiometry of Chemical Reactions", section 4.2 Classifying Chemical Reactions_