Answer : The correct option is, (a)
Explanation :
According to the Bronsted Lowry concept, Bronsted Lowry-acid is a substance that donates one or more hydrogen ion in a reaction and Bronsted Lowry-base is a substance that accepts one or more hydrogen ion in a reaction.
Or we can say that, conjugate acid is proton donor and conjugate base is proton acceptor.
(a) The equilibrium reaction will be,
![NH_4^++H_2O\rightleftharpoons NH_3+H_3O^+](https://tex.z-dn.net/?f=NH_4%5E%2B%2BH_2O%5Crightleftharpoons%20NH_3%2BH_3O%5E%2B)
In this reaction,
is an acid that donate a proton or hydrogen to
base and it forms
and
are conjugate base and acid respectively.
Thus,
is act as Brønsted-Lowry acid.
(b) The equilibrium reaction will be,
![NH_2^-+H_3O^+\rightleftharpoons NH_3+H_2O](https://tex.z-dn.net/?f=NH_2%5E-%2BH_3O%5E%2B%5Crightleftharpoons%20NH_3%2BH_2O)
In this reaction,
is an acid that donate a proton or hydrogen to
base and it forms
and
are conjugate acid and base respectively.
Thus,
is act as Brønsted-Lowry base.
(c) The equilibrium reaction will be,
![CN^-+H_3O^+\rightleftharpoons HCN+H_2O](https://tex.z-dn.net/?f=CN%5E-%2BH_3O%5E%2B%5Crightleftharpoons%20HCN%2BH_2O)
In this reaction,
is an acid that donate a proton or hydrogen to
base and it forms
and
are conjugate acid and base respectively.
Thus,
is act as Brønsted-Lowry base.
(d) The equilibrium reaction will be,
![F^-+H_3O^+\rightleftharpoons HF+H_2O](https://tex.z-dn.net/?f=F%5E-%2BH_3O%5E%2B%5Crightleftharpoons%20HF%2BH_2O)
In this reaction,
is an acid that donate a proton or hydrogen to
base and it forms
and
are conjugate acid and base respectively.
Thus,
is act as Brønsted-Lowry base.
(c) The equilibrium reaction will be,
![CH_3COO^-+H_3O^+\rightleftharpoons CH_3COOH+H_2O](https://tex.z-dn.net/?f=CH_3COO%5E-%2BH_3O%5E%2B%5Crightleftharpoons%20CH_3COOH%2BH_2O)
In this reaction,
is an acid that donate a proton or hydrogen to
base and it forms
and
are conjugate acid and base respectively.
Thus,
is act as Brønsted-Lowry base.
From this we conclude that that,
species could not react as a Brønsted-Lowry base.
Hence, the correct option is, (a) ![NH_4^+](https://tex.z-dn.net/?f=NH_4%5E%2B)