Final answer:
The contribution of water to the concentration of hydronium [] or hydroxide [] ions for a strong acid or base is negligible, as strong acids and bases dissociate almost completely in water.
Step-by-step explanation:
For a strong acid or base, the contribution of the water to the total [H₃O⁺] or [OH⁻] is negligible. This is because strong acids and bases dissociate almost completely in water.
Therefore, the concentration of hydronium ions [H₃O⁺] for strong acids, or the concentration of hydroxide ions [OH⁻] for strong bases, is effectively equal to the concentration of the strong acid or base itself. The additional contribution of H₃O⁺ or OH⁻ from the self-ionization of water is so small in comparison that it is typically ignored in calculations.