Three amphiprotic ions have the following second acid-dissociation constants at 25…

CHEMISTRY · Subjective · A Level · Chemistry · Acids and bases · Acids and bases

Problem

Three amphiprotic ions have the following second acid-dissociation constants at 25 °C: • HCO

_3^-

K_{a2} = 4.7\times10^{-11}

• H

_2

_4^-

K_{a2} = 6.2\times10^{-8}

• HS

^-

K_{a2} = 1.2\times10^{-13}

Using only these data, rank the ions HCO

_3^-

, H

_2

_4^-

, and HS

^-

from strongest to weakest base in water. Express your answer as “strongest > … > weakest” and briefly justify your ranking in one sentence.