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This chart shows the ranges of acid and base strength for each of the named solvents. The range from 0 to 14 in water is the standard pH scale.[1]

In chemistry, the leveling effect is the effect of a solvent (especially amphoteric solvents like water) on acids and bases that are dissolved in it.[2] A solution of an acid can't be stronger than the conjugate acid of the solvent, and a solution of a base can't be stronger than the conjugate base of the solvent.

The conjugate acid of the solvent is called the lyonium ion,[3] and the conjugate base is called the lyate ion.[4]

Examples

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Perchloric acid is a much stronger acid than hydrogen chloride in general. Both acids are stronger than the hydronium ion, which is the conjugate acid of water, so in a water solution, they completely react to make hydronium and their conjugate bases:

H2O + HCl → H3O+ + Cl−
H2O + HClO4 → H3O+ + ClO−4

Since the actual acid in the solution is hydronium, both solutions will be equally acidic, even though the pure compounds are very different.

A similar reaction occurs with bases. Sodium amide NaNH2 and sodium methoxide NaOCH3 are both one equivalent of different anionic bases, azanide and methoxide. Both of these bases are stronger than the hydroxide ion, which is the conjugate base of water. Just like with acids, these strong bases will react with water, making a solution of the bases' conjugate acids and sodium hydroxide:

H2O + NaNH2 → NaOH + NH3
H2O + NaOC2H5 → NaOH + CH3OH

Like with acids, these solutions will be equally basic in water despite azanide being much stronger than methoxide in general.

References

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  1. ↑ Atkins, P.W. (2010). Shriver and Atkins' Inorganic Chemistry, Fifth Edition. Oxford University Press. pp.121. ISBN978-1-42-921820-7.
  2. ↑ IUPAC, Compendium of Chemical Terminology, 5th ed. (the "Gold Book") (2025). Online version: (2006–) "Levelling effect". doi:10.1351/goldbook.L03506
  3. ↑ IUPAC, Compendium of Chemical Terminology, 5th ed. (the "Gold Book") (2025). Online version: (2006–) "Lyonium ion". doi:10.1351/goldbook.L03654
  4. ↑ IUPAC, Compendium of Chemical Terminology, 5th ed. (the "Gold Book") (2025). Online version: (2006–) "Lyate ion". doi:10.1351/goldbook.L03653
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