Which statement about weak electrolytes is true?

Which statement about weak electrolytes is true?

• A. They dissociate completely in water
• B. They do not dissociate in water at all
• C. They dissociate partially and reach equilibrium
• D. They are always acids or bases

Answer: (C)

Weak electrolytes ionize in water only to a limited extent, creating a dynamic balance between the undissociated molecules and the ions that are formed. Because only a small fraction dissociates, the solution contains relatively few ions, so it conducts electricity only weakly. This partial ionization is described by a dissociation equilibrium (and, for acids, by Ka; for bases, by Kb). An example is acetic acid, which largely remains as intact molecules but a small amount ionizes to form acetate ions and hydronium ions. The key idea is that the process does not go to completion; it reaches an equilibrium where ionization and recombination occur at equal rates.

Weak electrolytes ionize in water only to a limited extent, creating a dynamic balance between the undissociated molecules and the ions that are formed. Because only a small fraction dissociates, the solution contains relatively few ions, so it conducts electricity only weakly. This partial ionization is described by a dissociation equilibrium (and, for acids, by Ka; for bases, by Kb). An example is acetic acid, which largely remains as intact molecules but a small amount ionizes to form acetate ions and hydronium ions. The key idea is that the process does not go to completion; it reaches an equilibrium where ionization and recombination occur at equal rates.