In a chemical reaction, the law of conservation of mass states that matter is neither created nor destroyed. This means that the total mass of the reactants must equal the total mass of the products.
In the given reaction:
CaCO₃ → CO₂ + CaO
The scientist heats 30 grams of calcium carbonate (CaCO₃). According to the law of conservation of mass, the total mass of the products (CO₂ and CaO) will also be 30 grams.
Therefore, the total mass of the products is 30 grams.