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Solubility Rules

Soluble if Ksp > Q; insoluble if Q > Ksp
Quick Reference
Formula / NotationSoluble if Ksp > Q; insoluble if Q > Ksp
Also Known AsPrecipitation rules, ionic solubility guidelines, solubility table

What is Solubility Rules?

A set of generalizations about which ionic compounds are soluble in water. Most nitrates, group 1 salts, and ammonium salts are soluble. Most sulfates are soluble (except BaSO₄, PbSO₄). Most carbonates, phosphates, and hydroxides are insoluble (with exceptions).

Formula & Notation

Soluble if Ksp > Q; insoluble if Q > Ksp

Other Names / Synonyms: Precipitation rules, ionic solubility guidelines, solubility table

Properties & Characteristics

Solubility rules are empirical guidelines that predict whether a given ionic compound will dissolve in water based on the identities of the cation and anion. Common rules state that all nitrates and Group 1 metal salts are soluble, while most carbonates, phosphates, and sulfides are insoluble. The rules provide qualitative guidance based on patterns of solubility. They are supplemented by quantitative Ksp values for precise calculations.

Uses & Applications

Solubility rules are used in precipitation reactions to predict whether a precipitate will form when two salt solutions are mixed. They guide gravimetric analysis in quantitative analytical chemistry. In water treatment, solubility rules predict the removal of ions by precipitation.

Safety Information

Solubility rules help identify soluble forms of toxic heavy metals that may contaminate water supplies. Insoluble precipitates of toxic metals are generally less bioavailable but not necessarily safe.

Always consult the SDS/MSDS before handling any chemical. This information is for educational purposes only.

Key Facts

Term Solubility Rules
Formula Soluble if Ksp > Q; insoluble if Q > Ksp
Synonyms Precipitation rules, ionic solubility guidelines, solubility table

Frequently Asked Questions

A set of generalizations about which ionic compounds are soluble in water. Most nitrates, group 1 salts, and ammonium salts are soluble. Most sulfates are soluble (except BaSO₄, PbSO₄). Most carbonates, phosphates, and hydroxides are insoluble (with exceptions).

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