Electrolytes

Definition and Classification

Electrolytes are substances that, when dissolved in water, produce a solution that can conduct electricity due to the presence of ions. The ability of a solution to conduct electric current depends on the extent to which the solute dissociates into ions.

• Strong electrolytes: Dissociate completely in water, producing a high concentration of ions and conducting a strong electric current.

• Weak electrolytes: Only partially dissociate in water, resulting in fewer ions and a weak electric current.

• Nonelectrolytes: Do not dissociate into ions at all, so their solutions do not conduct electricity.

Example:

• Strong electrolyte: Sodium chloride (NaCl) in water dissociates completely:

• Weak electrolyte: Acetic acid (CH3COOH) in water partially dissociates:

• Nonelectrolyte: Sucrose (C12H22O11) in water does not dissociate: (no ions formed)

Electrolytes and Nonelectrolytes

Electrolyte Strength and Number of Ions

The strength of an electrolyte is determined by the number of ions it produces in solution. The more ions present, the greater the electrical conductivity.

• 1 mol of NaCl produces 2 mol of ions: 1 mol Na+ and 1 mol Cl-.

• 1 mol of Ca(OH)2 produces 3 mol of ions: 1 mol Ca2+ and 2 mol OH-.

• A solution of 1 mol Ca(OH)2 in 1 L is a stronger electrolyte than 1 mol NaCl in 1 L, due to more ions.

• 1 mol of any strong electrolyte in 1 L produces a greater current than 1 mol of any weak electrolyte in 1 L.

• 1 mol of a nonelectrolyte in 1 L does not produce a current.

Strong Electrolytes

Types and Identification

Strong electrolytes include strong acids, strong bases, and soluble ionic salts. It is essential to memorize the common strong acids and bases.

Additional info: The list above covers the seven common strong acids and the main strong bases. Sulfuric acid is strong only in its first dissociation.

Soluble Ionic Compounds and Exceptions

Most soluble ionic compounds are strong electrolytes, but there are important exceptions.

Additional info: These tables help predict solubility and thus electrolyte strength in aqueous solutions.