Final answer:
The value of Kb for the formate anion (HCOO−) is calculated using the Ka value for its conjugate acid and Kw, resulting in Kb = 4.76 × 10⁻¹¹.
Step-by-step explanation:
The value of Kb for the formate anion, HCOO−, can be determined using the known value for Ka of its conjugate acid (formic acid, HCOOH) and the autoionization constant of water (Kw). The formula used to find the base ionization constant (Kb) is:
Kb = Kw / Ka
Given:
- Kw = 1.0 × 10⁻¹⁴
- Ka(HCOOH) = 2.1 × 10⁻⁴
Using the formula:
Kb = (1.0 × 10⁻¹⁴) / (2.1 × 10⁻⁴) = 4.76 × 10⁻¹¹