An aqueous solution is prepared by dissolving 1350 mg1350\text{ mg}1350 mg of sodium hydrogensulfate (NaHSO4\text{NaHSO}_4NaHSO4) in water and making up to exactly 250 cm3250\text{ cm}^3250 cm3 of solution. The measured pH\text{pH}pH of this solution at 298 K298\text{ K}298 K is 1.851.851.85.
Calculate the value of KaK_{\text{a}}Ka for the hydrogensulfate ion (HSO4−\text{HSO}_4^-HSO4−) behaving as a weak acid in this solution. Give your answer to three significant figures. State the units of KaK_{\text{a}}Ka.
