Question

Which of the following is NOT a conjugate acid-base pair? 

(a ) NH4⁺/NH₂^-. 

(b) H₃O⁺/H₂O 

(c) H₂SO₃/HSO₃^- 

(d) C₂H₃O₂^- /HC₂H₃O₂ HC

(e) Cal All of the above are conjugate acid-base pairs.

Answer 1

Answer : - a) NH₄⁺ / NH₂^-

NH₄⁺ /NH₂^- is not a conjugate acid base pair.

since, this pair is differ by 2 protons.

1.  
H3O+ = H2O + H+
is conjugate acid- base pair.

Here, H₃O⁺ is a proton (H⁺) donar and act as an acid. While H₂O is a proton (H⁺) acceptor and act as base.

2.
H2SO3 = HSO3 + H+
is a conjugate acid-base pair.

Here, H₂SO₃ is a proton (H⁺) donor and act as acid. While HSO₃^- is a proton (H⁺) acceptor and act as base.

3.
HC2H302=C2H30, + H+
is a conjugate acid-base pair.

Here, HC₂H₃O₂ is a proton (H⁺) donor and act as an acid. While C₂H₃O₂^- is a proton (H⁺) acceptor and act as base.

Note:-

The chemical species whose formulae differ only by one proton are called conjugate acid-base pairs.

HCI+ NH3 = NH + C1-

In the above reaction, there are two conjugate acid-base pairs.

One HCl (acid-1) and Cl^-(base-1)

And another NH₄⁺ (acid-2) and NH₃ (base-2)

The members of each conjugate acid-base pair are designated by the same numerical subscript.