43. Solving a chemistry problem

4. To determine the content of sulfate ions in the water of a mineral spring, 25.00 ml of 0.1115 M BaCl2 was added to 150.0 ml of it. Without filtering the BaSO4 precipitate, an ammonium buffer containing magnesium complexonate was added to the mixture, and 14.00 ml of 0.01242 M EDTA was titrated. Calculate the concentration of sulfate ions (mg/l). Answer: 67.16 mg/l