What is the leveling effect again? I don't remember if we discussed it or not, because it's not anywhere in my notes.

The leveling effect is the phenomenon in which all acids stronger than the conjugate acid of the solvent are converted to that conjugate acid, and all bases stronger than the conjugate base of the solvent are converted to that conjugate base.

In water:

The conjugate acid of water is H₃O⁺ (hydronium ion).
→ Any acid stronger than H₃O⁺ (e.g., HCl, HNO₃, H₂SO₄) donates a proton to water, producing H₃O⁺.
→ Therefore, these acids all appear equally strong in aqueous solution.

The conjugate base of water is OH⁻ (hydroxide ion).
→ Any base stronger than OH⁻ (e.g., NH₂⁻, H⁻, CH₃⁻) reacts with water to form OH⁻.
→ Therefore, these bases all appear equally strong in aqueous solution.

In short: In water, the strongest acid that can exist is H₃O⁺ and the strongest base is OH⁻. Stronger acids/bases are "leveled down" to these limits.

thank you