In a chemical reaction, the law of conservation of mass states that the mass of the reactants must equal the mass of the products. This means that the total mass of the products will be equal to the total mass of the reactants.
Given that the scientist is heating 30 grams of calcium carbonate (CaCO3), the total mass of the products (CO2 and CaO) will also be 30 grams.
So, the total mass of the products is 30 grams.