Solid Mg(OH)2 is mixed with water and the following reversible reaction occurs:.
Mg(OH)2(s) Mg2+(aq) + 2OH-(aq), Kc1 = 1.8 x 10-11
After some time, the system reaches a state of dynamic equilibrium. Which chemical species are present at equilibrium in this system?

Mg^2+ and OH- are the chemical species present at the equilibrium. Mg(OH)2 will not affect the equilibrium.

Explanation:

Step 1: data given

Reactants are Solid Mg(OH)2 and H2O(l)

Kc1 = 1.8 * 10^-11

Step 2: The balanced equation

Mg(OH)2(s)  ⇄ Mg2+(aq) + 2OH-(aq)

Step 3: Define the equilibrium constant Kc

Kc = [OH-]²[Mg^2+]

Pure solids and liquids do not have any effect or influence on the equilibrium in the reaction. So they are not included in the equilibrium constant expression.

This means Mg^2+ and OH- are the chemical species present at the equilibrium. Mg(OH)2 will not affect the equilibrium.