Acid/Base Ionization Constants

K_a values for some common acids

Name	Formula	Ka	pKa
acetic acid	CH3COOH	1.8 × 10-5	4.74
acrylic acid	CH2CHCOOH	5.6 × 10-5	4.25
benzoic acid	C6H5COOH	6.4 × 10-5	4.19
boric acid	H3BO3	5.8 × 10-10	9.24
butanoic acid	CH3CH2CH2COOH	1.5 × 10-5	4.82
chloroacetic acid	CH2ClCOOH	1.4 × 10-3	2.85
chlorous acid	HClO2	1.2 × 10-2	1.92
formic acid	HCOOH	1.8 × 10-4	3.74
hydrocyanic acid	HCN	6.2 × 10-10	9.21
hydrofluoric acid	HF	6.3 × 10-4	3.20
hydrogen peroxide	H2O2	2.4 × 10-12	11.62
hypobromous acid	HBrO	2.0 × 10-9	8.70
hypochlorous acid	HClO	3.5 × 10-8	7.46
hypoiodous acid	HIO	2.0 × 10-11	10.70
lactic acid	CH3CH(OH)COOH	1.38 × 10-4	3.86
nitrous acid	HNO2	4.0 × 10-4	3.40
phenol	C6H5OH	1.6 × 10-10	9.80
propanoic acid	CH3CH2COOH	1.3 × 10-5	4.89
trichloroacetic acid	CCl3COOH	2.2 × 10-1	0.66

K_b values for some common bases

Name	Formula	Kb	pKb
ammonia	NH3	1.8 × 10-5	4.74
aniline	C6H5NH2	4.3 × 10-10	9.37
dimethylamine	(CH3)2NH	5.4 × 10-4	3.27
ethylamine	C2H5NH2	5.6 × 10-4	3.25
hydrazine	NH2NH2	1.7 × 10-6	5.77
hydroxylamine	NH2OH	1.1 × 10-8	7.96
methylamine	CH3NH2	4.38 × 10-4	3.36
nicotine	C10H14N2	1.0 × 10-6	6.00
piperidine	C5H10NH	1.3 × 10-3	2.89
propylamine	C3H7NH2	3.7 × 10-4	3.43
pyridine	C5H5N	1.8 × 10-9	8.74
triethylamine	(C2H5)3N	1.0 × 10-3	3.00
trimethylamine	(CH3)3N	6.5 × 10-5	4.19

K_a values for some polyprotic acids

Name	Formula	Ka	pKa
arsenic acid	H2AsO4	1) 5.0 × 10-3 2) 9.3 × 10-8 3) 3.0 × 10-12	1) 2.30 2) 7.03 3) 11.52
carbonic acid	H2CO3	1) 4.3 × 10-7 2) 5.6 × 10-11	1) 6.37 2) 10.25
citric acid	H3C6H5O6	1) 8.4 × 10-4 2) 1.8 × 10-5 3) 4.0 × 10-6	1) 3.08 2) 4.74 3) 5.40
oxalic acid	H2C2O4	1) 6.5 × 10-2 2) 6.1 × 10-5	1) 1.19 2) 4.21
phosphoric acid	H3PO4	1) 7.5 × 10-3 2) 6.2 × 10-8 3) 4.8 × 10-13	1) 2.12 2) 7.21 3) 12.32
sulfuric acid	H2SO4	1) ~100 2) 1.2 × 10-2	1) -2 2) 1.92
sulfurous acid	H2SO3	1) 1.5 × 10-2 2) 1.0 × 10-7	1) 1.82 2) 7.00