Question

What is the conjugate acid of each of the following? What is the conjugate base of each?

Answer 1

Answer:

a. H₂O (conjugate acid) ; b. OH⁻ (conjugate base), H₃O⁺ (conjugate acid) ; c. H₂CO₃ (conjugate acid), CO₃⁻² (conjugate base) ; d. NH₄⁺ (conjugate strong acid) e. H₂SO₄ (conjugate acid), SO₄⁻² (conjugate base) ; f. No conjugate acid either base;  g. H₂S (conjugate acid), S⁻² (conjugate base);

h. H₄N₂ (conjugate base)

Explanation:

a.  OH⁻  +  H⁺  ⇄ H₂O

The hydroxide acts like a Bronsted Lory base, so it can catch a proton. Water will be the conjugate acid.

b. H₂O, is an amphoterus compound. It can act as an acid or a base. If it is a base, the conjugate acid is the H₃O⁺. If it is an acid, the conjugate base is the OH⁻.

c. HCO₃⁻  +  H⁺  ⇄  H₂CO₃

HCO₃⁻  +  H₂O  ⇄ CO₃⁻²  +  H₃O⁺

The bicarbonate is also amphoteric. When it catches the proton, the carbonic acid is the conjugate acid, cause it works as a base.

When the HCO₃⁻ (acid) release the proton, the conjugate base is the carbonate.

d. Ammonia is a weak base, so the conjugate strong acid is the ammonium.

NH₃ + H₂O  ⇄  NH₄⁺  +  OH⁻

e. Another amphoteric compound. The acid sulfate acts an acid and a base.

(like bicarbonate). When it is a base, the conjugate acid is the sulfuric acid, when it is an acid, the conjugate base is the sulfate.

HSO₄⁻  +  H₂O  ⇄  SO₄⁻²  +  H₃O⁺

HSO₄⁻  +  H⁺  ⇄  H₂SO₄

f. H₂O₂ does not recieve H⁺ or OH⁻, and it does not release H⁺. It is a neutral compound and it doesn't act as a base or acid.

g. HS⁻ is amphoterous.

HS⁻  +  H⁺  ⇄  H₂S

HS⁻  +  H₂O  ⇄  S⁻²  +  H₃O⁺

Same case as bicarbonate or acid sulfate.

h. H₅N₂⁺  +  H₂O  ⇄  H₄N₂  + H₃O⁺

Hidrazinium acts an acid, so, the conjugate base will be the hidrazine.