Add one of the following: barium chloride, barium hydroxide, barium nitrateObservation with potassium nitrate: colourless solution/ or no visible change or reaction) Observation with potassium sulfate: white precipitate formation
Explanation for understanding: This question refers to the solubilities of group 2 compounds. In general, group 2 nitrate compounds are soluble, hence why no precipitate is formed in the reaction with potassium nitrate, where barium nitrate is formed The solubility of group 2 sulfates decreases down the group so in the reaction with potassium sulfate, barium sulfate is formed which is highly insoluble (it is further down in the group) so a visible white precipitation is observed