Kps = [Mg2+][OH-]2

pH = 14- pOH = 14 -10 = 4

[OH-] = 10-pOH = 1∙10-4

Kps = s ∙ [OH-]2 = 3,4∙10-3 ∙ (1∙10-4)2 = 3,4∙10-11