Definition of Levelling Effect
The term levelling effect is also known as solvent levelling is defined as the effect a solvent has on the properties of acids as well as of bases. The level of acidity is often limited by the basicity of the solvent. On the other hand, the strength of a strong base is levelled by the acidity of the solvent.
Take an example of a strong acid HA which when dissolved in water reacts to give hydronium ion (H3O+). When ammonia (NH3) is a solvent, the strongest acid is ammonium (NH4+). On the contrary, OH- is known to be the strongest of the bases.