According to the Law of Conservation of Mass, the total mass of reactants equals the total mass of products. In this reaction, we have:
- Mass of carbon = 24 g
- Mass of oxygen = 16 g
The total mass of the reactants is:
\[ 24 , \text{g} + 16 , \text{g} = 40 , \text{g} \]
This total mass will be equal to the mass of the carbon dioxide (CO2) formed. Therefore, the mass of carbon dioxide formed is:
\[ \text{Mass of CO2} = 40 , \text{g} \]
So the correct answer is 40 g.