Solubility of salts. Determination of the solubility of salts

The solubility of salts is related to the ability of these compounds to dissolve in water. Whenever we refer to the solubility of a salt, the solvent used will be water.

is called salt the compound that in water undergoes the phenomenon of dissociation, releasing a cation other than hydronium (H₃O⁺) and an anion other than hydroxyl (OH^-). See the dissociation of NaCl in water:

NaCl_(here) → In⁺_(here) + Cl^-_(here)

About solubility, we can classify salts into two large groups:

• soluble salt (salt that has good solubility in water);

• practically insoluble salt (salt that dissolves in an extremely negligible amount in water, but some kind of dissolution occurs, however small it may be).

To determine the solubility of salts in water, it is enough to know the anion present in the salt. See the rules that address the types of anions:

• Nitrate (AT THE₃^-) and nitrite (AT THE₂^-): all salt containing these anions are soluble;

• Carbonate (CO₃^-2), Phosphate (DUST₄^-3) and Sulfide (s^-2): soluble only with members of the IA family and with the NH₄⁺;

• Halides (F^-, Cl^-, br^-, I^-): with Ag cations⁺ Ass^+,, hg₂⁺² and Pb⁺², are insoluble;

• Acetate (H₃Ç₂O₂^-): with Ag cations⁺ and hg₂⁺², it is insoluble;

• Sulfate (ONLY₄^-2): with Ag cations⁺, alkaline earth metals (IIA, except magnesium), Hg₂⁺² and Pb⁺², it is insoluble;

• Any other anion:soluble only with members of the IA family and with the NH₄⁺.

See some examples of determining the solubility of salts:

1st) NH₄br

This salt has a halide (Br) accompanied by the NH group₄⁺. For this reason, it is a soluble salt, since the halide only forms practically insoluble salt with the Ag groups.⁺, ass^+,, hg₂⁺² and Pb⁺².

2) (NH₄)₃DUST₄

This salt has a phosphate(DUST₄^-3) accompanied by the group NH₄⁺. For this reason, it is a soluble salt, since phosphate only forms soluble salt with NH groups₄ ⁺ and alkali metals (AI).

3) In₂ONLY₄

This salt has a sulfate (ONLY₄^-2) accompanied by the group At⁺ (alkali metal). For this reason, it is a soluble salt, since sulfate only forms insoluble salt with NH groups₄ ⁺, Ag cations⁺, alkaline earth metals (IIA, except magnesium), Hg₂⁺² and Pb⁺².

By Me. Diogo Lopes Dias

Source: Brazil School - https://brasilescola.uol.com.br/quimica/solubilidade-dos-sais.htm