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Dissociation constant

In chemistry and biochemistry the dissociation constant, abbreviated Kd, is a measure of the extent to which a dissociation reaction

AB ↔ A + B

proceeds at equilibrium.

It is given quantitatively by the expression

Kd = [A]×[B]×[AB]-1

Where [A], [B], and [AB] indicate the concentrations of A, B, and AB, respectively.

See also hydrogen bond.

The dissociation constant is a specific type of equilibrium constant.

The dissociation constant of water (Ke) varies in function of the temperature. The value of pH for neutrality is not the same at different temperatures.

water Ke pKe
0°C 0.1e-14 14.92
10°C 0.3 14.52
18°C 0.7 14.16
25°C 1.2 13.92
30°C 1.8 13.75
50°C 8 13.10
60°C 12.6 12.90
70°C 21.2 12.67
80°C 35 12.46
90°C 53 12.28
100°C 73 12.14