Orders of magnitude in pH

Definition

Each one-unit change in pH represents a tenfold change in both hydrogen and hydroxide concentrations in opposite directions. Across pH 0 to 14 hydrogen concentration swings by a factor of a hundred trillion.

The scale compresses enormous chemical shifts into small numbers, so small pH moves can hide enormous chemical changes. Moving from pH 2.5 to 3.5 cut hydrogen by 90 percent while appearing to move only one point, and reaching 13.4 redistributed molecular populations by orders of magnitude. Worked values show pH 2.5 at 3.2 times 10 to the minus 3 mol/L hydrogen and pH 13.4 at 2.5 times 10 to the minus 1 mol/L hydroxide.

Related concepts

Logarithmic scale · pH as equilibrium position · Over-neutralization

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Part of The Blueprint of Water · 📏 measurement