Chemistry

The key insight is that in basic solutions, $[OH^-]$ tells you directly how many hydroxide ions are present—you just need to convert that to $pH$ using the relationship between $pOH$ and $pH$. Start by finding $pOH$ from $[OH^-]$ using the definition $pOH = -\log[OH^-]$, then use the water equilibrium constant to find $pH = 14 - pOH$. This two-step process bridges the world of hydroxide concentration to the familiar $pH$ scale.

The key insight is that in basic solutions, $[OH^-]$ tells you directly how many hydroxide ions are present—you just need to convert that to $pH$ using the relationship between $pOH$ and $pH$. Start by finding $pOH$ from $[OH^-]$ using the definition $pOH = -\log[OH^-]$, then use the water equilibrium constant to find $pH = 14 - pOH$. This two-step process bridges the world of hydroxide concentration to the familiar $pH$ scale.