Which acid is the best choice to create a buffer with pH=pH = 2.07? Which acid is the best choice to create a buffer with 2.07? chlorous acid (HClO2), pKa=1.95 (HClO2), pKa=1.95 hypochlorous acid (HClO), pKa=7.54 (HClO), pKa=7.54 nitrous acid (HNO2), pKa=3.34 (HNO2), pKa=3.34 acetic acid (HCH3CO2), pKa=4.76

The best choice to create a buffer with pH = 2.07 is chlorous acid

Explanation:

To choose the pH of a buffer you must know that the nearest pH to pKa of the buffer, the better buffer capacity (quantitative measure of the resistance to change of pH of a buffer)

If you see, in the problem, the acid that has the pKa nearest to desire pH (2.07), is chlorous acid (HClO₂; pKa = 1.95). Thus, the best choice to create a buffer with pH = 2.07 is chlorous acid.