insoluble

(adjective)

That which cannot be dissolved.

Related Terms

Examples of insoluble in the following topics:

  • Precipitation Reactions

    • Precipitation reactions transform ions into an insoluble salt in aqueous solution.
    • Precipitation refers to a chemical reaction that occurs in aqueous solution when two ions bond together to form an insoluble salt, which is known as the precipitate.
    • A precipitation reaction can occur when two solutions containing different salts are mixed, and a cation/anion pair in the resulting combined solution forms an insoluble salt; this salt then precipitates out of solution.
    • To determine the solubility of an given salt, find the cationic component along the left-hand side, match it to the anionic component along the top, then check to see if it is S - soluble, I - insoluble, or sS - slightly soluble.

  • Solubility

    • The term "insoluble" is often applied to poorly soluble compounds.
    • In contrast, a non-polar solute such as naphthalene is insoluble in water, moderately soluble in methanol, and highly soluble in benzene.
    • Carbonates, hydroxides, sulfates, phosphates, and heavy metal salts are often insoluble.
    • The solubilities of salts formed from cations on the left and anions on the top are designated as: soluble (S), insoluble (I), or slightly soluble (sS).
    • Recognize the various ions that cause a salt to generally be soluble/insoluble in water.

  • Predicting Precipitation Reactions

    • Note that soluble compounds will dissolve in water and insoluble compounds will not.
    • Carbonates (CO32-): All are insoluble except those of potassium (K+), sodium (Na+), and ammonium (NH4+).
    • Salts of phosphates (PO43-), oxalates (C2O42-), chromates (CrO42-), and sulfides (S2-): Generally insoluble.
    • The product that forms may be insoluble, in which case a precipitate will form, or soluble, in which case the solution will be clear.
    • You know that sodium chloride (NaCl) is soluble in water, so the remaining product (copper carbonate) must be the one that is insoluble.

  • Properties of Sulfur

    • Sulfur burns with blue flame, is insoluble in water, and forms polyatomic allotropes.
    • Sulfur is insoluble in water but soluble in carbon disulfide and, to a lesser extent, in other nonpolar organic solvents, such as benzene and toluene.

  • Chemical Analysis

    • Those that form insoluble chlorides, such as lead, silver, and mercury.
    • Those that form acid-insoluble sulfides, such as cadmium, bismuth, copper, antimony, and tin.
    • Those that form insoluble hydroxide complexes, such as iron, aluminum, and chromium.
    • A group of insoluble carbonate salts.

  • Carbon Oxides and Carbonates

    • Most salts are insoluble in water, with solubility constants (Ksp) less than 1 x 10-8, with the exception of lithium, sodium, potassium, and ammonium carbonates.
    • Although the carbonate salts of most metals are insoluble in water, this is not true of the bicarbonate salts.
    • Under changing temperature or pressure, and in the presence of metal ions with insoluble carbonates, the equilibrium between carbonate, bicarbonate, carbon dioxide, and carbonic acid in water can result in the formation of insoluble compounds.

  • Solutions and Heats of Hydration

    • Since the coulombic forces that bind ions and highly polar molecules into solids are quite strong, we might expect these solids to be insoluble in most solvents.
    • Ionic solids are insoluble in the majority of non-aqueous solvents, but they tend to have high solubility specifically in water.
    • In fact, some compounds are strictly insoluble due to their high lattice energies that cannot be overcome to form a solution.

  • Soaps & Detergents

    • Fatty acids made up of ten or more carbon atoms are nearly insoluble in water, and because of their lower density, float on the surface when mixed with water.
    • To summarize, the presence of a soap or a detergent in water facilitates the wetting of all parts of the object to be cleaned, and removes water-insoluble dirt by incorporation in micelles.
    • If the pH of a soap solution is lowered by acidic contaminants, insoluble fatty acids precipitate and form a scum.

  • Solid Solubility and Temperature

    • During recrystallization, an impure substance is taken up in a volume of solvent at a temperature at which it is insoluble, which is then heated until it becomes soluble.

  • Water Solubility

    • Many organic compounds, especially alkanes and other hydrocarbons, are nearly insoluble in water.