In an experiment to measure K_sp of CaSO₄ [D. Masterman, j. Chem. Educ., 64, 409 (1987)], a saturated solution of CaSO₄(aq) is poured into the ion-exchange column pictured. As the solution passes through the column, Ca²⁺ is retained by the ion-exchange medium and H₃O⁺ is released; two H₃O⁺ ions appear in the effluent solution for every Ca²⁺ ion. As the drawing suggests, a 25.00 mL sample is added to the column, and the effluent is collected and diluted to 100.0 mL in a volumetric flask. A 10.00 mL portion of the diluted solution requires 8.25 mL of 0.0105 M NaOH for its titration. Use these data to obtain a value of K_sp for CaSO₄.

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010 25.00 mL satd CaSO4(aq) + water 100.0 mL- 8.25 mL 0.0105 M NaOH- 10.00 mL