the Keq of Mg(OH)2 is 2(10^-11). calculate the concentration of Mg ions in a saturated solution of this compound

Answer 1

Usually this is called Ksp.

..........Mg(OH)2 ==> Mg^2+ + 2OH^-
I.........solid.......0.........0
C.........solid.......x.........2x
E.........solid.......x.........2x

Plug the E line into the Ksp expression and solve for x = (Mg^2+)