Acid dissociation constant
Thermodynamics
An equilibrium constant is related to the standard Gibbs energy change for the reaction, so for an acid dissociation constant.

Acid dissociation constant

Section Title: Thermodynamics
Table Section Text: An equilibrium constant is related to the standard Gibbs energy change for the reaction, so for an acid dissociation constant.

Compound	Equilibrium	pKa	ΔG⊖ (kJ·mol−1)	ΔH⊖ (kJ·mol−1)	−TΔS⊖ (kJ·mol−1)

HA = Acetic acid	HA ⇌ H+ + A−	4.756	27.147	−0.41	27.56

H2A+ = GlycineH+	H2A+ ⇌ HA + H+	2.351	13.420	4.00	9.419

HA ⇌ H+ + A−	9.78	55.825	44.20	11.6

H2A = Maleic acid	H2A ⇌ HA− + H+	1.92	10.76	1.10	9.85

HA− ⇌ H+ + A2−	6.27	35.79	−3.60	39.4

H3A = Citric acid	H3A ⇌ H2A− + H+	3.128	17.855	4.07	13.78

H2A− ⇌ HA2− + H+	4.76	27.176	2.23	24.9

HA2− ⇌ A3− + H+	6.40	36.509	−3.38	39.9

H3A = Boric acid	H3A ⇌ H2A− + H+	9.237	52.725	13.80	38.92

H3A = Phosphoric acid	H3A ⇌ H2A− + H+	2.148	12.261	−8.00	20.26

H2A− ⇌ HA2− + H+	7.20	41.087	3.60	37.5

HA2− ⇌ A3− + H+	12.35	80.49	16.00	54.49

HA− = Hydrogen sulfate	HA− ⇌ A2− + H+	1.99	11.36	−22.40	33.74

H2A = Oxalic acid	H2A ⇌ HA− + H+	1.27	7.27	−3.90	11.15

HA− ⇌ A2− + H+	4.266	24.351	−7.00	31.35

Sentence(s)

Oxalic acid has pKₐ value of 1.27.

final_sentence: Oxalic acid has pKₐ value of 1.27.