Table 2. pKa values for various acids
REAGENT
pKa1
pKa2
pKa3
Acetic Acid (CH3COOH)
4.756
-
-
Citric Acid
3.128
4.761
6.396
Carbonic Acid (H2CO3)
6.351
10.329
-
Phosphoric Acid (H3PO4)
2.148
7.198
12.375
Sulfuric Acid (H2SO4)
-
-
1.987
Phthalic Acid (C6H4(CO2H)2)
2.950
5.408
-