Which pair of compounds is soluble in water?

Step 2: Analyze each pair of compounds by applying common solubility rules: for example, most chlorides (Cl⁻) are soluble except those of Ag⁺, Pb²⁺, and Hg₂²⁺; most sulfates (SO₄²⁻) are soluble except those of Ba²⁺, Pb²⁺, and Ca²⁺; most hydroxides (OH⁻) are insoluble except those of alkali metals and some alkaline earth metals; most sulfides (S²⁻) and carbonates (CO₃²⁻) are generally insoluble except with alkali metals and ammonium.