Chapter 7 · Chemical Reactions
7.5Aqueous Solutions and Solubility
11 min · two checks
Predict
Will silver chloride dissolve appreciably in water?
The idea
- Describe what (aq) means at the ion level.
- Apply a basic set of solubility rules.
An aqueous solution has water as the solvent. Soluble ionic compounds dissociate: the ions separate and move among water molecules. Insoluble ones do not dissolve enough to matter in these problems, so if they would form, they form a solid instead. “Insoluble” here means very low solubility, not a mathematical zero.
A working rule set: nitrates and Group 1 and ammonium compounds are soluble. Most chlorides, bromides, and iodides are soluble except those of Ag⁺, Pb²⁺, and Hg₂²⁺. Most sulfates are soluble except those of Ba²⁺, Sr²⁺, Pb²⁺, and Ca²⁺. Hydroxides are insoluble except Group 1 and somewhat Ba²⁺, Sr²⁺, and Ca²⁺. Carbonates, phosphates, and sulfides are insoluble except Group 1 and ammonium. You will use these rules to predict precipitates.
Keep these
- (aq) ionic compounds are separated ions.
- Group 1, ammonium, and nitrates: soluble.
- The famous chloride exceptions are silver, lead, and mercury(I).