Answer to Question #101409 in General Chemistry for Noboku

Question

1. How does the solubility constant relate to the equilibrium constant?

2. The first step in the preparation of magnesium metal is the precipitation of Mg(OH)2 from sea water by the addition of Ca(OH)2. The concentration of Mg2+(aq) in sea water is 5.37 × 10–2 M. Calculate the [OH-] at which [Mg2+] is diminished to 1.0 × 10–5 M by the addition of Ca(OH)2.

Answer 1

1. The solubility constant is the equilibrium constant for reaction of dissolving.

For example, reaction Mg(OH)₂ = Mg²⁺ + 2OH^-

K_sp (solubility constant) = [Mg²⁺][OH^-]²

2. K_sp(Mg(OH)₂) = 5.6×10^-12

[OH^-]=7.5×10^-4 mol l^-1