A strong base in water dissociates completely to give a high concentration of hydroxide ions, while a weak base dissociates only partially, yielding far fewer hydroxide ions under the same conditions. This difference in ionization extent is the key factor that distinguishes their ion concentrations and, in turn, the pH of their solutions.

Core idea

• Strong base: complete ionization
  • Example: NaOH completely dissociates in aqueous solution: NaOH → Na⁺ + OH⁻
  • Result: high [OH⁻], higher pH (closer to 14) for a given total base concentration.

• Weak base: partial ionization
  • Example: NH₃ in water establishes equilibrium NH₃ + H₂O ⇌ NH₄⁺ + OH⁻
  • Result: lower [OH⁻] than a strong base of the same nominal concentration; pH is above 7 but not as high as with a strong base.

Practical implications

• Degree of dissociation correlates with the base’s strength constant (Kb). A larger Kb means a stronger base and greater dissociation, thus higher [OH⁻] at a given concentration.

• In solutions with identical nominal concentrations, strong bases produce more ions and conduct electricity more readily than weak bases.

If you’d like, I can walk through a sample calculation comparing a strong base like NaOH to a weak base like NH₃ at the same formal concentration, showing the resulting [OH⁻], pH, and how the equilibrium shifts in each case.