The amount of calcium present in milk can be determined by adding oxalate to a sample and measuring the mass of calcium oxalate precipitated. What is the mass percent of calcium if 0.429 g of calcium oxalate forms in a 125-g sample of milk when excess aqueous sodium oxalate is added? Na₂C₂O₄(aq) + Ca²⁺(aq) → CaC₂O₄(s) + 2Na⁺(aq)

Question

Quizplus · Accepted Answer

The molar mass of calcium oxalate (CaC2O4) is approximately 128.1 g/mol, and the molar mass of calcium (Ca) is about 40.08 g/mol. The mass of calcium in 0.429 g of calcium oxalate is (40.08/128.1) * 0.429 g = 0.134 g. The mass percent of calcium is (0.134 g / 125 g) * 100% = 0.107%.

The Amount of Calcium Present in Milk Can Be Determined