Question

6. Enough of a sparingly soluble salt AB(s) dissolved in a certain amount of water to bring it into equilibrium with the ions A" (aq) and B (aq). If the equilibrium concentration of A*? is 4.9 x 10 mol kg"', and the Debye Hückel Limiting Law (DHLL) is obeyed at this concentration, K sp for the salt is: A) 2.11e-9 B) 4.90e-9 C) 4.86e-10 D) 8.46e-9 E) 3.91e-10

Answer 1

According to the dissolution equation,

AB $\rightarrow$ A²⁺ + B^2-

We see that molarity of A²⁺ = Molarity of B^2-

[B^2-] = 4.9 * 10^-5

Now: K_sp = [A₂₊] * [B^2-] = 4.9 * 10^-5 * 4.9 * 10^-5 = 2.40 * 10^-9 M²