### The p-values pKA and pKB

mathematically:            p...... = -log .......

KA and KB are the acid / base constants, who's values can be find in tables.
Often the values of concentrations (certainly the mathematical products of concentrations) are extremely small, like for example: 10-6 mol/l.
Therefore were introduced the so called p-values; they make writing of and calculating with concentrations a lot easier.

KA and KB also often have very small values, like: 10-12 or 10-7
In chemical calculations and in the books we use the p-values 12 or 7

In aqueous neutral solutions with a temperature of 25ºC:
• data: [H3O+] = [OH-] = 10-7 mol/dm3       i.e.;     pH = pOH = 7
• Kw (constant of the autoprotolysis) = K x (55.6)2 = [H3O+] x [OH-] = 10-14

The following statement is true: pKw = pH + pOH

pKW at 25ºC has a value of ±14; at 100ºC that value is ±12

### pH

Study the following scheme; try to understand it and to explain:

 pH -1 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 pOH 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 -1 very strong and/or concentrated acid solutions acid solutions neutral solutions basic solutions very strong and/or concentrated basic solutions