How many ionization constants are associated with oxalic acid (h2c2o4)?

Two.

Explanation: Number of ionization constants associated with an acid equals to the number of hydrogen ions(protons) that it produces in aqueous solution.

For example, HCl is a monoprotic acid as it produces only one hydrogen ion in aqueous solution and so only one ionization constant is associated with it.

(sulfuric acid) is a diprotic acid as it produces two hydrogen ions in aqueous solution and hence there are two ionization constant values associated with this.

Similarly, Oxalic acid is also a diprotic acid and so two ionization constant values are associated with this.

The two ionization equations of oxalic acid are as follows:-

and are the two ionization constants for first and second equations respectively.