69. To determine the calcium carbonate (CaCO3) content in a 500.0 mg solid sample, a chemist prepared two identical flasks (sample flask and blank flask), each containing exactly the same volume and concentration of hydrochloric acid (HCl). For sample flask, 500.0 mg sample was added, allowing the CaCO3 to react completely with the HCl. For the blank flask, no sample was added; this flask represents the total initial amount of HCl. After the reaction completed, the acid in both flasks was titrated with 0.1000 M NaOH. The blank flask required 45.00 mL of NaOH, while the sample flask required 25.00 mL of NaOH. What is the mass of CaCO3 in the sample? (Molar mass of CaCO3 = 100.0 g/mol)
(A) 50.0 mg
(B) 100.0 mg
(C) 200.0 mg
(D) 250.0 mg
(E) 450.0 mg

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統計: A(0), B(1), C(0), D(0), E(0) #3854091