Leveling Effect (chemistry)
Leveling effect or solvent leveling refers to the effect of solvent on the properties of acids and bases. The strength of a strong acid is limited ("leveled") by the basicity of the solvent. Similarly the strength of a strong base is leveled by the acidity of the solvent. When a strong acid is dissolved in water, it reacts with it to form hydronium ion (H3O+) in the following reaction:
- HCl + H2O → Cl- + H3O+
Any acid that is stronger than H3O+ reacts with H2O to form H3O+. Therefore, no acid stronger than H3O+ exists in H2O. Similarly, when ammonia is the solvent, the strongest acid is ammonium (NH4+), thus HCl and a super acid exert the same acidifying effect.
The same argument applies to bases. In water, OH- is the strongest base. Thus, even though sodium amide (NaNH2) is an exceptional base (pKa of NH3 ~ 33), in water it is only as good as sodium hydroxide. On the other hand, NaNH2 is a far more basic reagent in ammonia than is NaOH.
Read more about Leveling Effect (chemistry): Leveling and Differentiating Solvents
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