Here's why:
* pH and pOH: pH and pOH are related by the equation: pH + pOH = 14. This means that as pH increases, pOH decreases.
* pOH and [OH-]: pOH is the negative logarithm of the hydroxide ion concentration ([OH-]): pOH = -log[OH-]. Therefore, a lower pOH indicates a higher [OH-].
Putting it together:
* A high pH means a low pOH.
* A low pOH means a high [OH-].
Therefore, the highest pH value corresponds to the highest concentration of hydroxide ions.
