An aqueous solution is prepared by dissolving 1920 mg of potassium hydrogen oxalate (KHC2O4\text{KHC}_2\text{O}_4KHC2O4) in water and making up to exactly 500 cm3 of solution. The measured pH\text{pH}pH of this solution at 298 K is 2.15.
Calculate the value of KaK_{\text{a}}Ka for the hydrogen oxalate ion (HC2O4−\text{HC}_2\text{O}_4^-HC2O4−) behaving as a weak acid in this solution. Give your answer to three significant figures. State the units of KaK_{\text{a}}Ka.
