Beginner Topic 726 of 1102 Inorganic Chemistry
Solubility Rules
Guidelines for predicting whether ionic compounds dissolve in water.
In-depth explanation of Solubility Rules
Solubility rules are general guidelines that predict whether an ionic compound will dissolve in water, saving the need to memorize every solubility. Nitrates, salts of Group 1 metals and ammonium salts are soluble. Chlorides, bromides and iodides are soluble except those of silver, lead(II) and mercury(I). Sulfates are soluble except those of barium, lead and, to a lesser extent, calcium and strontium. Carbonates, phosphates, hydroxides and sulfides are generally insoluble, except with Group 1 metals or ammonium. These rules are approximate, and temperature also matters.
Going deeper: Solubility Rules
Key ideas: Always soluble: Group 1 and NH4+ salts, nitrates, acetates, chlorates, perchlorates. Chlorides, bromides, iodides soluble except Ag+, Pb2+, Hg2 2+ (PbCl2 slightly). Sulfates soluble except Ba2+, Sr2+, Pb2+ and slightly Ca2+, Ag+. Hydroxides, carbonates, phosphates, sulfides and chromates are insoluble except group 1 and NH4+ (and Ba(OH)2, Ca(OH)2 slightly; sulfides of Ca, Sr, Ba soluble-ish). Soluble means above about 0.1 mol per L.
Common mistakes and connections: Students apply rules as absolutes, but slightly soluble compounds exist and Ksp gives the quantitative answer. Do not assume that insoluble means zero. Mixed compounds like AgCl dissolve with NH3 by complexation. Predict precipitation by comparing Q to Ksp. Links to precipitation reactions, Ksp, qualitative analysis and net ionic equations.
Visualization of Solubility Rules
Solubility product values show which salts are sparingly soluble: a smaller Ksp such as BaSO4 means a more insoluble compound. The interactive lesson shows this as a live animation or chart.
Worked example and use case
Barium sulfate is insoluble, so mixing barium chloride with sodium sulfate forms a white precipitate.
Frequently asked questions about Solubility Rules
What is Solubility Rules?
Guidelines for predicting whether ionic compounds dissolve in water.
Is Solubility Rules a beginner, intermediate or advanced topic?
Solubility Rules is a beginner topic in Inorganic Chemistry. It needs no earlier chemistry lessons and is a good starting point.
What should I learn before Solubility Rules?
Study these earlier topics in Inorganic Chemistry first: Hydrates, Types of Chemical Reactions, Activity Series of Metals.
What comes after Solubility Rules?
The next topics in Inorganic Chemistry are Precipitation Reactions and Net Ionic Equations.
Can I practise Solubility Rules with quizzes?
Yes. The interactive lesson includes a self-check question on Solubility Rules, and the Inorganic Chemistry quiz draws on every topic in this area.
Where Solubility Rules fits in Inorganic Chemistry
Solubility Rules is topic 111 of 113 in Inorganic Chemistry.