pK

K

Often the values of concentrations (certainly the mathematical products of concentrations) are extremely small, like for example: 10

Therefore were introduced the so called p-values; they make writing of and calculating with concentrations a lot easier.

K

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: [H
_{3}O^{+}] = [OH^{-}] = 10^{-7}mol/dm^{3}i.e.; pH = pOH = 7 - K
_{w}(constant of the autoprotolysis) = K*x*(55.6)^{2}= [H_{3}O^{+}]*x*[OH^{-}] = 10^{-14}

The following statement is true: pK

pK

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 |