Hydrogen cyanide, hcn, is a weak acid. which equation best represents its aqueous chemistry?

The equations are as follow,

A) HCN (aq) + H₂O (l) ↔ H₂CN⁺ (aq) + OH⁻ (aq)

B) H₂O (l) ↔ H⁺ (aq) + OH⁻ (aq)

C) HCN (aq) ↔ H⁺ (aq) + CN⁻ (aq)

D) HCN (aq) + H₂O (l) ↔ CN⁻ (aq) + H₃O⁺ (aq)

E) HCN (aq) ↔ H⁻ (aq) + CN⁺ (aq)

Answer:

Option-D is the correct answer.

Explanation:

When hydrogen cyanide is added in water it partially ionizes as follow,

HCN (aq) + H₂O (l) ↔ CN⁻ (aq) + H₃O⁺ (aq)

Being weak acid it fails to completely dissociate into H⁺ and CN⁻ ions. In this reaction water is acting as a Bronsted Lowery Base and picks proton from from HCN and converts into conjugate acid (i. e. H₃O⁺), while, HCN converts into conjugate Base (i. e. CN⁻).