Question

Strength of acid-base is influenced by solvent water. Select the correct statement(s) about the levelling effect of water on strength of acid-bases. (This question has multiple correct options)
A. $N{H_2}$and ${H^ - }$ in water show levelling effect and have same base strength
B. Acids which are weaker than ${H_3}{O^ + }$ are not levelled by water
C. Bases which are stronger than $O{H^ - }$ are levelled by water
D. Acids and bases are also levelled in the same characteristics solvents other than water

Answer 1

The levelling effect of a solvent is used to compare the acidic or basic strength of the acids or base. The levelling effect is not shown by all solvent. Since water shows levelling effect, thus we can compare the acidic or basic strength with the help of ${H_3}{O^ + }$ and $O{H^ - }$ ions respectively.

Complete answer:
The question is completely related to levelling effect of acid and base. The acidity or basicity of acid or base also depends on the solvent. This is the basic principle of leveling effect. According to this, the strength of acid can be leveled by the basicity of the solvent. Similarly we can say that the strength of base can be levelled by acidity of solvent. When we dissolve a strong acid in water solvent then it forms ${H_3}{O^ + }$ions. Thus any acid which is stronger than ${H_3}{O^ + }$ will react with water and form ${H_3}{O^ + }$ ions. Therefore we can say that no acid stronger than ${H_3}{O^ + }$ ion can exist in water solvent. Now we can say that, when ammonia is a solvent, the strongest acid will be ammonium ion and hence $HCl$ exert the same effect. The same condition is for bases also. Hence we can say that the basicity of the solvent will level the strength of strong acid and acidity of the solvent will level the strength of weak acid. Therefore, acids which are stronger than ${H_3}{O^ + }$ and the bases which are stronger than $O{H^ - }$ will be levelled by water solvent. Therefore $N{H_2}$and ${H^ - }$ show levelling effects and have the same base strength. Other solvents like ammonia also show this levelling effect. Therefore we can say that all the given options are correct. All these options are valid statements for levelling effect.
Hence, option A,B , C and D all are correct.

Note:
The levelling effect is also known as the solvent effect of acid-base. This effect is only valid for some solvent like water and ammonia. For acidity we compare ${H_3}{O^ + }$ of the acids and for base we compare $O{H^ - }$ ions of base. This effect is only used to determine the strength of acids and base.