NaOH is a strong base which means that it dissociates completely in water. It will break apart into Na⁺ and OH⁻ ions.
NaOH ⇒ Na⁺ + OH⁻
Because NaOH dissociates completely into its respective ions in water, the moles of NaOH is equal to the moles of hydroxide ions. So, [OH⁻] = 0.0001 M.
Now to find the pOH, use the formula pOH = -log[OH⁻].
