Ka and pKa
for Polyprotic Acids
| Acid Name |
|
Ka |
pKa |
| Carbonic, H2CO3 |
1st |
4.5 x 10-7 |
6.35 |
|
2nd |
4.7 x 10-11 |
10.33 |
| Hydrogen sulphide, H2S |
1st |
9.5 x 10-8 |
7.02 |
|
2nd |
1.0 x 10-19 |
19.0 |
| Phosphoric acid, H3PO4 |
1st |
7.1 x 10-3 |
2.15 |
|
2nd |
6.3 x 10-8 |
7.20 |
|
3rd |
4.5 x 10-13 |
12.35 |
| Sulphuric acid, H2SO4 |
1st |
large |
|
|
2nd |
1.2 x 10-2 |
1.92 |
| Telluric acid, H6TeO6 |
1st |
2.0 x 10-8 |
7.7 |
|
2nd |
1.0 x 10-11 |
11.0 |
|
3rd |
3.0 x 10-15 |
14.5 |
| Sulphurous acid, H2SO3 |
1st |
1.2 x 10-2 |
1.92 |
|
2nd |
6.6 x 10-8 |
7.18 |
| Selenous acid, H2SeO3 |
1st |
3.5 x 10-3 |
2.46 |
|
2nd |
5.0 x 10-8 |
7.3 |
| Tellurous acid, H2TeO3 |
1st |
3.0 x 10-3 |
2.5 |
|
2nd |
2.0 x 10-8 |
7.7 |
| Ascorbic acid, H2C6H6O6 |
1st |
7.9 x 10-5 |
4.10 |
|
2nd |
1.6 x 10-12 |
11.79 |
| Citric acid, H3C6H5O7 |
1st |
7.1 x 10-4 |
3.15 |
|
2nd |
1.7 x 10-5 |
4.77 |
|
3rd |
6.4 x 10-6 |
5.19 |