What is the concentration of OH- in a 0.359M solution of Mg(OH)2?

Answer 1

M = mole / V consider the volume is constant

Mg(OH)₂ ------> Mg²⁺ + 2 OH^-

the mole ratio is 1:2

the concentration of OH^- = 2 x 0.359 = 0.718 M