You are given a sample of limestone, which is mostly CaCO3, to determine the mass percentage of

Question:

You are given a sample of limestone, which is mostly CaCO3, to determine the mass percentage of Ca in the rock. You dissolve the limestone in hydrochloric acid, which gives a solution of calcium chloride. Then you precipitate the calcium ion in solution by adding sodium oxalate, Na2C2O4. The precipitate is calcium oxalate, CaC2O4. You find that a sample of limestone weighing 128.3 mg gives 140.2 mg of CaC2O4. What is the mass percentage of calcium in the limestone?