Chart: Acid Ionization Constants

**Acid Ionization Constants at 25°C**
Name of Acid	Ionization Equation	$K_a$
Sulfuric acid	$text{H}_2text{SO}_4 rightleftarrows text{H}^+ + text{HSO}^-_4$ $text{HSO}^-_4 rightleftarrows text{H}^+ + text{SO}^{2-}_4$	very large $1.3 times 10^{-2}$
Oxalic acid	$text{H}_2text{C}_2text{O}_4 rightleftarrows text{H}^+ + text{HC}_2text{O}^-_4$ $HC_2O^-_4 rightleftarrows H^+ + C_2O^{2-}_4$	$6.5 times 10^{-2}$ $6.1 times 10^{-5}$
Phosphoric acid	$text{H}_3text{PO}_4 rightleftarrows text{H}^+ + text{H}_2text{PO}^-_4$ $text{H}_2text{PO}_4^- rightleftarrows text{H}^+ + text{HPO}^{2-}_4$ $HPO^{2-}_4 rightleftarrows H^+ + PO^{3-}_4$	$7.5 times 10^{-3}$ $6.2 times 10^{-8}$ $4.8 times 10^{-13}$
Hydrofluoric acid	$text{HF} rightleftarrows text{H}^+ + text{F}^-$	$7.1 times 10^{-4}$
Nitrous acid	$text{HNO}_2 rightleftarrows text{H}^+ + text{NO}^-_2$	$4.5 times 10^{-4}$
Benzoic acid	$text{C}_6text{H}_5text{COOH} rightleftarrows text{H}^+ + text{C}_6text{H}_5text{COO}^-$	$6.5 times 10^{-5}$
Acetic acid	$text{CH}_3text{COOH} rightleftarrows text{H}^+ + text{CH}_3text{COO}^-$	$1.8 times 10^{-5}$
Carbonic acid	$text{H}_2text{CO}_3 rightleftarrows text{H}^+ + text{HCO}^-_3$ $text{HCO}^-_3 rightleftarrows text{H}^+ + text{CO}^{2-}_3$	$4.2 times 10^{-7}$ $4.8 times 10^{-11}$
Hydrocyanic acid	$text{HCN} rightleftarrows text{H}^+ + text{CN}^-$	$4.9 times 10^{-10}$

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