Solubility Rules - Chemistry LibreTexts

Understanding Solubility

• Solubility: Maximum concentration of a solute that can dissolve in a solvent.
• Types of Solutions:
  1. Dilute Solution: Contains less solute than the maximum solubility.
  2. Saturated Solution: Contains solute equal to its solubility.
  3. Supersaturated Solution: Contains more solute than can be dissolved, leading to crystallization and precipitation.

Solubility Rules

• Rules help determine solubility of ionic solids.
• If rules contradict, precedence is given to the earlier rule.

Key Solubility Rules

1. Group I Salts:

   • Soluble (Li+, Na+, K+, Cs+, Rb+).
   • Ammonium ion (NH4+) salts are soluble.

2. Nitrate Ion (NO3-):

   • Generally soluble.

3. Halides (Cl-, Br-, I-):

   • Generally soluble.
   • Exceptions: Halides of Ag+, Pb2+, (Hg2)2+ are insoluble (e.g., AgCl, PbBr2).

4. Silver Salts:

   • Mostly insoluble.
   • Exceptions: AgNO3 and Ag(C2H3O2) are soluble.

5. Sulfate Salts:

   • Generally soluble.
   • Exceptions: CaSO4, BaSO4, PbSO4, Ag2SO4, SrSO4 are insoluble.

6. Hydroxide Salts:

   • Slightly soluble.
   • Group I hydroxides are soluble.
   • Group II hydroxides (Ca, Sr, Ba) are slightly soluble.
   • Hydroxides of transition metals and Al3+ are insoluble (e.g., Fe(OH)3).

7. Sulfides:

   • Transition metal sulfides (e.g., CdS, FeS) are insoluble.
   • Arsenic, antimony, bismuth, lead sulfides are insoluble.

8. Carbonates:

   • Generally insoluble.
   • Exceptions: Group II (CaCO3, SrCO3) and FeCO3, PbCO3.

9. Chromates:

   • Generally insoluble (e.g., PbCrO4).

10. Phosphates:

    • Generally insoluble (e.g., Ca3(PO4)2).

11. Fluorides:

    • Generally insoluble (e.g., BaF2, MgF2).

Applications in Reactions

• Solubility impacts precipitation in reactions.
• Precipitation occurs when products formed in a reaction are insoluble.

Practice Problems

1. FeCO3 Solubility:

   • Likely to form a precipitate due to carbonate rule.

2. ClO4- Solubility:

   • Likely soluble; does not form a precipitate.

3. Precipitate Formation:

   • CaSO4 and AgBr likely to form precipitates.
   • NaCl remains soluble.

4. Reaction Precipitation:

   • Ag2S forms a precipitate; NaNO3 remains soluble.

5. Reaction without Precipitate:

   • Both KOH and Na2CrO4 are soluble; no precipitate forms.

References

• Books and resources for further reading on solubility and related chemistry topics.

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Note: The content is licensed under CC BY 4.0 and authored by Antoinette Mursa & Kenneth W. Busch.