Self-ionization of Water - Isotope Effects

Isotope Effects

Heavy water, D2O, self-ionizes less than normal water, H2O; oxygen forms a slightly stronger bond to deuterium because the larger mass of deuterium difference results in a lower zero-point energy, a quantum mechanical effect. The following table compares the values of pKw for H2O and D2O.

pKw values for pure water
T/°C 10 20 25 30 40 50
H2O 14.535 14.167 13.997 13.830 13.535 13.262
D2O 15.439 15.049 14.869 14.699 14.385 14.103

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