Calculating pH

The pH scale is estimated from the concentration of hydrogen ions.

pH = - log [H⁺] p H equals minus logarithm of proton concentration

For strong acids and bases, [H⁺] the concentration of protons can be directly derived from the concentration of the acid or base.

For weak acids and bases, the [H⁺] needs to be calculated from the K_athe concentration of protons needs to be calculated from the acid dissociation constant .

K_a = ( [H⁺] [A^¯] ) / [HA] the acid dissociation constant equals the concentration of protons times the concentration of the conjugated base, divided by the concentration of the acid

For buffers, the pH can be calculated using the Henderson-Hasselbalch equation.