Question

Which of the following is NOT an acid-base conjugate pair?
a.NH4+ and NH3
b.H2O and OH-
c.H2S and OH-
d.H2CO3 and HCO3-
e.none of the above

Answer 1

Answer : The option (c) does not show an acid-base conjugate pair.

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,

$NH_3+H_2O\rightleftharpoons NH_4^++OH^-$

In this reaction, $NH_3$ and $H_2O$ are acid and base and $NH_4^+$ and $OH^-$ are conjugate acid and base respectively.

(b) The equilibrium reaction will be,

$H_2O+H_2O\rightleftharpoons H_3O^++OH^-$

In this reaction, $H_2O$ and $H_2O$ are acid and base and $H_3O^+$ and $OH^-$ are conjugate acid and base respectively.

(c) The equilibrium reaction will be,

$H_2S+H_2O\rightleftharpoons H_3O^++HS^-$

In this reaction, $H_2S$ and $H_2O$ are acid and base and $H_3O^+$ and $HS^-$ are conjugate acid and base respectively.

(d) The equilibrium reaction will be,

$HCO_3^-+H_2O\rightleftharpoons H_2CO_3+OH^-$

In this reaction, $HCO_3^-$ and $H_2O$ are base and acid and $H_CO_3$ and $OH^-$ are conjugate acid and base respectively.

Hence, from this we conclude that, the option (c) does not show an acid-base conjugate pair.