Leveling Effect Definition:

Levelling or solvent leveling is an effect that prevents a strong acid or base to exist in a solution.

Leveling Effect Explained:

Leveling is easily explained when we use water as the solvent. In this case, the effect will prevent bases stronger than hydroxide to exist in solution. The strong base will cease to exist by itself and will be completely deprotonated to form a hydroxide ion and the respective cation. Hence, no base stronger than the OH– can be used when the solvent is water. In terms of base strength, this means that all bases greater in strength than the hydroxide ion tend to be indistinguishable in strength when in aqueous solution.

Levelling effect is also witnessed when using other solvents such that, in the said solvent, the base ceases to exist. Example – the effect prevents having a base stronger than an amide ion in liquid ammonia. Hence, we must use a solvent that cannot be readily deprotonated.

Furthermore, leveling effect is also true for acids in solution. Example – aqueous solutions of a strong acid result in the formation of high concentrations of the hydronium ion. Therefore, no acid stronger than the hydronium ion (H3O+) exists in water.Look at the example for sulphuric acid below. In terms of acid strength, this means that all acids greater in strength than the hydronium ion tend to be indistinguishable in strength when in aqueous solution.