Question #600ea

1 Answer
Apr 7, 2014

Almost all polyatomic ions are soluble in water when paired with the correct cation or anion.

The real question is, "What polyatomic ions can stay in aqueous solution with their partner ions?"

We use the solubility rules to answer this question.

  1. All compounds of Group 1 metals are soluble. This includes polyatomic anions.

  2. All ammonium (NH₄⁺) salts are soluble. This includes polyatomic anions.

  3. All nitrates (NO₃⁻), chlorates (ClO₃⁻), perchlorates (ClO₄⁻), and acetates (CH₃COO⁻) are soluble

  4. The chloride (Cl⁻), bromide (Br⁻), and Iodide (I⁻) salts of Hg₂²⁺ are insoluble.

  5. All sulfates (SO₄²⁻) are soluble except those of Ba²⁺, Sr²⁺, Ca²⁺, Pb²⁺, Hg₂²⁺ and Hg².

  6. All hydroxides (OH⁻) are insoluble except those of Group 1 metals and Ba²⁺, Sr²⁺, and Ca²⁺.

  7. All sulfites (SO₃²⁻), carbonates (CO₃²⁻), chromates (CrO₄²⁻), and phosphates (PO₄³⁻) are insoluble. Exceptions are these compounds with NH₄⁺ and Group 1 metals.