1. To observe the electrical conductivity of various pure liquids, ionic solids, metals and aqueous
solutions using a conductivity probe and LED conductivity indicator.
2. To classify substances as strong, weak or nonelectrolytes.
3. To observe the changes in conductivity during the course of double displacement reactions.
a. Ionic compounds, in the solid state, are composed of ions that are not free to move. The ions
become mobile after the compound is heated to its melting temperature, becomes fluid, and the ions are
freed from their positions in their crystalline lattice. The large number of mobile ions then causes the
molten compounds to become good electrical conductors.
b. Covalent compounds do not conduct electricity even when molten because the resultant mobile
particles are neutral molecules. Their movement cannot be used to carry an electric charge.
Metals conduct electricity in the solid state because the valence electrons of the atoms generate a mobile
“sea” of electrons.
Water is a good solvent for many covalent and ionic compounds. Substances that dissolve in water to
form electrically conducting solutions are electrolytes. Substances that dissolve to form nonconducting
solutions are known as nonelectrolytes. All soluble ionic compounds are electrolytes. Water molecules
are able to pull the positively and the negatively charged ions away from each other in the solid state, and
carry them along to be distributed throughout the solution.
NaCl (s)
!"#
Na+
(aq) + Cl- (aq)
Most covalent compounds are nonelectrolytes. When dissolved, molecules of covalent compounds are
separated from each other by water molecules. The separated molecules are not charged species and will
not conduct electricity. However, some covalent compounds actually react with water to form ions. The
process of forming ions in this manner is known as ionization.
HCl (g) + H2O (l) à H3O+
(aq) + Cl- (aq)
If all dissolved molecules react to form ions, the solution becomes strongly conducting and the solutes are
referred to as strong electrolytes. If only a fraction of the dissolved molecules ionizes the solution
becomes weakly conducting and the compound is known as a weak electrolyte.
HC2H3O2 (aq) + H2O (l) à H3O+
(aq) + C2H3O2
- (aq)
Explanation:
