Calculating the Decomposition of CaCO3 Calcium carbonate (CaCO3), an important component of coral reefs, can decompose when heated, forming calcium oxide (CaO) and carbon dioxide (CO2) according to the equation below: CaCO3 es002-1. Jpg CaO CO2 How many moles of CaO form when 98. 60 g CaCO3 decompose? 98. 60 g CaCO3 = 0. 9851 mol CaO To determine the mass of CO2 that forms from a given mass of CaCO3, which of the following must be known? Check all that apply. Molar mass of CaCO3 molar mass of CaO mole ratio of CaCO3 to CO2 mole ratio of CaO to CO2 molar mass of CO2 mass of CaO formed.