The best way to express the concentration of hydroxyl ions is in terms of pH and pOH.
pOH = -log [OH-]
Also, for aqueous solution, pH + pOH = 14. Also, if pH of solution is more than 7, it is basic in nature.
Given: [OH-] = 1x10⁻⁴m
∴ pOH = -log [10^-4] = 4
and pH = 14 - 4 = 10
