Conjugate Acids and Conjugate Bases For Various Compounds
Conjugate acid Formula Structure pKa Conjugate base Name
Methane CH4 50-60 Methyl
Ethene CH2CH2 45 Ethenyl
Ammonia NH3 36 Amide
Acetylene (ethyne) C2H2 26 Acetylide
Ethanol C2H5OH 16 Ethoxide
Water HOH 15.7 Hydroxide
Ammonium NH4+ HNH3 9.8 : NH3 Ammonia
Hydroflouric acid HF 4 Flouride

Use this table to predict which conjugate base will favorably react with which conjugate acids. Pay attention to the pKa values shown. As a general rule, the conjugate base of any acid will react with, and remove, the proton (H+ ion) from any conjugate acid that is stronger than the conjugate acid from which the conjugate base you are looking at was derived from. 

In the chart above, the conjugate base will remove a proton from every conjugate acid that is below it in the table.


When I write quantitatively I mean that there is enough difference in the pKa values (of the conjugate acids) to remove greater than 99% of the protons from the acids below them. A difference of 2 pKa values will allow the conjugate base coming from the weaker acid will remove >99% of protons from the stronger acid.