Oxalate - Relationship To Oxalic Acid

Relationship To Oxalic Acid

The dissociation of protons from oxalic acid proceeds in a stepwise manner as for other polyprotic acids. Loss of a single proton results in the monovalent hydrogenoxalate anion HC₂O₄−. A salt with this anion is sometimes called an acid oxalate, monobasic oxalate, or hydrogen oxalate. The equilibrium constant (K_a) for loss of the first proton is 5.37×10−2 (pK_a = 1.27). The loss of the second proton, which yields the oxalate ion has an equilibrium constant of 5.25×10−5 (pK_a = 4.28). These values imply that, in solutions with neutral pH, there is no oxalic acid, and only trace amounts of hydrogen oxalate. The literature is often unclear on the distinction between H₂C₂O₄, HC₂O₄-, and C₂O₄2-, and the collection of species is referred to oxalic acid.