Question

Carbonic acid (HzCO3) and ammonium hydroxide (NH40H) soltions are weak electrolytes. However, when the two solutions are mixed and tested in the conductivity apparatus, the bulb glows brightly. a) Briefly explain this phenomenon. (0.05 pt) b) Write balanced chemical equation of this reaction. (0 025 po c) Write net ionic equation af this reaction. (0.025 pt

Answer 1

Electrical conductivity in solutions

1. Electrical conductivity of molten compounds
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.
2. Electrical conductivity of metallic solids
Metals conduct electricity in the solid state because the valence electrons of the atoms generate a mobile
“sea” of electrons.
3. Electrical conductivity of compounds in aqueous solutions
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) ----------------> 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) ------------> H3O+(aq) + C2H3O2- (aq)

Principles behind conductivity apparatus

• Free electrons (as in a metal), free ions, or some other mobile charge carrier must be available to sustain an electric current. A solution that contains ions will conduct electricity. The amount of electricity that will flow through a solution depends primarily on the numbers of ions present: the greater the number of ions, the greater the amount of electricity which will flow. This can be observed by using a conductivity apparatus. The amount of electricity flowing is indicated by the brightness of the light bulb, the LED, or the meter reading.
• A strong electrolyte ionizes to a large degree. When a strong electrolyte is also soluble, its solutions contain many ions, conduct electricity well, and cause the lamps in a conductivity apparatus to burn brightly. A weak electrolyte dissociates only slightly in solution, forms fewer ions, and causes the light bulb to glow dimly. A nonelectrolyte has very few ions, and the light bulb will not glow. In this experiment the conductivity apparatus allows us to distinguish between strong and weak acids or bases.
• Acids and bases react to form salts and water. Salts are nearly always strong electrolytes.

"Electrical conductivity of molten compounds 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. 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. Electrical conductivity of metallic solids Metals conduct electricity in the solid state because the valence electrons of the atoms generate a mobile ""sea"" of electrons. Electrical conductivity of compounds in aqueous solutions 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. "