The base constant ( K B ) is a material constant and indicates the extent to which a base reacts alkaline in water. It is rarely used because it can be calculated directly from the acid constant K S of the corresponding acid. The following applies: the smaller the p K B value, the stronger the tendency of the base to take up protons. For acids and bases dissolved in water , with the dissociation equilibrium of water at 25 ° C, neglecting the fugacities, the following approximation applies :
Since the concentration of water remains practically constant during the reaction, it can be included in the constant . This finally gives the base constant :
The negative decadic logarithm of , the so-called -value, is often given:
For the value and the analogously defined value, the following applies at room temperature:
A table with many values and values can be found in the acid constant .
Individual evidence
↑ Gerhard Schulze, Jürgen Simon: Jander year measurement analysis , 17th edition, de Gruyter, Berlin, 2009, p. 79 f.
^ Karl-Heinz Lautenschläger, Werner Schröter, Joachim Teschner, Hildegard Bibrack: Taschenbuch der Chemie , 18th edition, Harri Deutsch, Frankfurt (Main), 2001, p. 186 f.