Final answer:
The Kb value for the conjugate base of HCN is 2.04 × 10⁻µ when Ka for HCN is 4.9 × 10⁻¹⁰ and the Kw of water is 1.0 × 10⁻¹⁴.
Step-by-step explanation:
The value of Kb for the conjugate base of HCN, given that the Ka for HCN is 4.9 × 10⁻¹⁰, can be calculated using the relation Ka × Kb = Kw, where Kw is the ionization constant of water. At 25 °C, Kw is equal to 1.0 × 10⁻¹⁴. Therefore, the Kb for the conjugate base of HCN is determined by rearranging the expression as Kb = Kw / Ka.
Using the given values: Kb = (1.0 × 10⁻¹⁴) / (4.9 × 10⁻¹⁰)
Kb = 2.04 × 10⁻µ for the conjugate base of HCN.