Question

Levelling effect is minimum in which of the following?
(A) Water
(B) DMSO
(C) Acetic acid
(D) Liquid ammonia

Answer 1

Hint: The levelling effect will be minimum in the solvent which is amphiprotic in nature. It always dissociates into hydronium and hydroxyl ions when a strong acid or base is added to it respectively.

Complete step by step solution:
The levelling effect is the restriction caused by the solvent to determine the acidic strength and the basic strength of strong acid and base respectively. This happens mostly in the amphiprotic solvent such as water.
Water acts as an amphiprotic solvent that means it can both accept and donate a proton. When different strong acids dissolve in water, the water behaves as a strong base and produces hydronium ions, ${{\text{H}}_{3}}{{\text{O}}^{+}}$, with each acid. Thus, the strength of every strong acid will be at the same “level” when dissolved in water and so we cannot study the acidic strength of different acids in water. This effect is known as Levelling effect.
Now, any solvent which can easily differentiate between the acidic or basic strength of different acids and bases will show a higher levelling effect.
In the given question, the water has the minimum levelling effect because we have already discussed that it acts as an amphiprotic solvent and it always forms hydronium ions and hydroxyl ions with every
strong acid and strong base respectively.

Additional information: Water is known as a universal solvent as well as a levelling solvent.

Hence, the correct answer is (A) Water.

Note: By saying that the acidic or basic strength of strong acids and bases are always the same in water, we mean that the degree of dissociation always comes out to be 1 in the case of water as a solvent.