One pH Unit Change

Quantifies the logarithmic trap: each single step on the pH scale is a tenfold change in hydrogen concentration (and a tenfold opposite change in hydroxide).

$$\Delta \mathrm{pH}=1\Rightarrow [{\mathrm{H}}^{+}]\text{changes by}10\times$$

Variables

Symbol	Meaning	Unit
$\Delta \mathrm{pH}$	Change in pH units	dimensionless
$[{\mathrm{H}}^{+}]$	Hydrogen-ion concentration	mol/L

Worked example

Moving from pH 2.5 to pH 3.5 drops [H+] from 3.2 x 10^-3 to 3.2 x 10^-4 mol/L, a 90% reduction even though pH moved only one point.

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Part of The Blueprint of Water