KOH is a strong base that dissociates completely in water:
\[\text{KOH} \rightarrow \text{K}^+ + \text{OH}^-\]
For a 0.001 M KOH solution, the concentration of hydroxide ions is:
\[[\text{OH}^-] = 0.001\;\text{M} = 10^{-3}\;\text{M}\]
First, calculate the pOH:
\[\text{pOH} = -\log[\text{OH}^-] = -\log(10^{-3}) = 3\]
Then, use the relationship between pH and pOH at 25 \(^\circ\)C:
\[\text{pH} + \text{pOH} = 14\]
\[\text{pH} = 14 - 3 = 11\]
The pH of 0.001 M KOH solution is 11.
Exam tip: For strong bases, first find [OH-] from the molarity, calculate pOH, then subtract from 14 to get pH. A pH of 11 confirms a basic solution, which is consistent with KOH being a strong alkali.
