So I was teaching my students... ""Now the pOH is simple calculated by pKw- pH, where pKw is 14 at STP. If you have the hydroxide concentration, then you can express it in a logarithmic formula shown as. pOH = -log[ OH^- ]. Remember! [ OH^- ] * [ H^+ ] =1 x10^-14 is useful when figuring out unknown values."" One of my student looks at me all blanked eye. ""I don't understand this at all."" ""You should. I mean, after all it's just basic chemistry!""