Solution Formation

Key Questions

  • Answer:

    Clearly the identity of both the solute and the solvent affect solution formation.


    The most common solvent is water. Why? For a start it covers 2/3 of the planet. Water is an exceptionally good solvent for ionic species, because it can solvate ions to form #Na^+(aq)# and #Cl^(-)(aq)#.

    The #(aq)# designation refers to the aquated ion; in solution this means the ion is surrounded by, or aquated by approx. 6 water molecules, i.e. #[Na(OH_2)_6]^+#. Water is exceptionally good at dissolving SOME ionic species because it can solvate ions; but some ion pairs i.e #AgCl# have little solubility in water. Water is conceived to have a partially negative central oxygen atom, bound to partially positive hydrogen atoms. This charge separation is referred to as polarity and allows ion solvation, and water is the best example of a polar solvent.

    Hexanes is a non-polar solvent. Hexanes will dissolve ethanol (#C_2H_5OH#), but not methanol (#H_3COH#). Why not?

  • A solution is a homogeneous mixture of two or more substances.

    There are many types of solutions.

    Gas in Gas

    • Air — oxygen and other gases dissolved in nitrogen.

    Gas in Liquid

    • Fish tank — oxygen in water.
    • Carbonated beverages — carbon dioxide in water.
    • Blood — oxygen and carbon dioxide are essential components of blood chemistry.

    Liquid in Liquid

    • Windshield washer fluid — methanol in water.
    • Alcoholic beverages — ethanol and other solutes in water.
    • Vinegar — acetic acid in water.

    Solid in Liquid

    • Maple syrup — sugar in water
    • Brine — salt in water.
    • Body fluids — complex aqueous solutions of sugar, urea, electrolytes, and many other solutes.

    Gas in Solid

    • Hydrogen dissolves rather well in palladium and tin.

    Liquid in Solid

    • Dental amalgam — mercury in silver, tin, and copper.
    • Hexane in paraffin wax

    Solid in Solid

    • Steel — carbon atoms in a crystalline matrix of iron atoms.
    • Bronze — copper and tin.
    • Brass — copper and zinc.