pH vs pOH: What's the Difference?
You've got comfortable with pH, and then a question asks for pOH and it feels like a whole new topic. It isn't. pOH is the same idea pointed at the other ion, and the two are locked together by one equation. The short answer: pH measures the concentration of hydrogen ions (H⁺) in a solution, while pOH measures the concentration of hydroxide ions (OH⁻). In water at 25 °C they are always linked by pH + pOH = 14 , so knowing either one gives you the other by subtraction. Quick comparison at a glance Feature pH pOH Measures H⁺ concentration OH⁻ concentration Formula pH = −log[H⁺] pOH = −log[OH⁻] Low value means Acidic Basic (alkaline) High value means Basic (alkaline) Acidic Neutral water at 25 °C 7 7 Typical range 0–14 14–0 Which is quoted in daily life Almost always this one Rarely Relationship pH + pOH = 14 pH + pOH = 14 What pH is pH is the negative logarithm of the hydrogen ion concentration: pH = −log[H⁺] The log is what makes the scale manageable. Hydroge...