What is the ka reaction of hcn? the ka of hcn is 6.2 à - 10-10. what is kb value for cnâ€" at 25°c?

The Ka reaction for HCN: HCN (aq) + H₂O (l) ⇄ CN⁻ (aq) + H₃O⁺ (aq)

or HCN (aq) ⇄ CN⁻ (aq) + H⁺ (aq).

Ka (HCN) = 6,2·10⁻¹⁰.

Ka · Kb = Kw; the ionic product of water.

6,2·10⁻¹⁰ mol/dm³ · Kb = 1·10⁻¹⁴ mol²/dm⁶; the ionic product of water at 25°C.

Kb (CN⁻) = 1·10⁻¹⁴ mol²/dm⁶ : 6,2·10⁻¹⁰ mol/dm³.

Kb (CN⁻) = 1,6·10⁻⁵ mol/dm³.