AP Chemistry Unit 3.7 Solutions and Mixtures

Water: The Universal Solvent

  • Water is a very versatile solvent because polar molecules are attracted to other polar molecules + its molecules form HB (adhesive)
    • (+) and (-) attraction
  • Why are ionic compounds soluble in water?
    • When ionic compounds are dissolved, the dipole of the water interacts with the charged ions and causes them to separate
    • The strong forces present among the positive and negative ions of the solid are replaced by stronger ion-dipole interactions → the interaction is energetically favorable
  • Hydration: “positive ends” of the water molecules are attracted to the negatively charged anions and that the “negative ends” are attracted to the positively charged cations
  • When ionic substances (salts) dissolve in water, they break up into the individual cations and anions.

The Nature of Aqueous Solutions: Strong and Weak Electrolytes

  • Electrical conductivity: its ability to conduct an electric current
  • Electrolyte: compound that conducts an electric current when dissolved in water or melted
    • Has charged particles

Strong Electrolytes

  • Strong electrolytes: substances that completely ionizes when they are dissolved in water (NaCl)
    • All ionic compounds and strong acids are strong electrolytes
  • Aqueous solutions with them conduct an electric current very efficiently

Weak Electrolytes

  • Weak electrolytes: only a few ions produced when dissolved in water (ex: acetic acid)
    • Solutions with them conduct only a small current
    • Weak acid (NH4+ ammonium ion)/base (NH3 ammonia) = weak electrolyte


  • Nonelectrolyte: substances that dissolves in water but do not produce any ions (ex: sugar, ethanol) → instead entire molecules dispersed in the water → solution does not conduct an electric current
Scroll to Top