Question

Determine el Kb de CN⁻ a 25°C. El Ka para HCN es 4.9 x 10⁻¹⁰.

a.1.4 x 10⁻⁵
b. 2.0 x 10⁻⁵
c. 4.9 x 10⁻¹⁴
d. 3.7 x 10⁻⁷

Answer 1

The Kb of CN⁻ at 25°C can be calculated by using the ionization constant (Ka) for HCN and the ionization constant of water (Kw). Following the equation Ka x Kb = Kw, substituting the values we can find the Kb of CN⁻ to be approximately 2.04 x 10⁻⁵.

Step-by-step explanation:

The ionization constant of HCN is given as 4.9 × 10-10 in Appendix H. To find the ionization constant for the conjugate base, CN-, we can use the relationship between Ka and Kb:

Ka x Kb = Kw, where Kw is the ionization constant of water (1.0 x 10-14).

Plugging in the given Ka value for HCN, we can solve for Kb:

Ka x Kb = Kw,

4.9 x 10-10 x Kb = 1.0 x 10-14,

Kb = (1.0 x 10-14) / (4.9 x 10-10),

Kb = 2.04 x 10-5.

So, the Kb of CN- at 25°C is approximately 2.04 x 10-5 (option b).