Dolomite is mixture of CaCO3 and MgCO3. When 1.000 g sample of this limestone is decomposed by heating, .268 L of Cao2 is produced measured @ 750. Torr and 20 C. Heating a metallic carbonate always produces carbon dioxide and a metallic oxide. It was determined that the original sample of the limestone contained 160.0 mg of calcium. What was the % by mass of CaCO3 in the original sample.