A 24.2219 g sample of impure magnesium car- bonate was heated to complete decomposition according to the equation MgCO3(s) = MgO(s) + CO2(g) . After the reaction was complete, the solid residue (consisting of MgO and the original impurities) had a mass of 17.0117 g. Assum- ing that only the magnesium carbonate had decomposed, how much magnesium carbon- ate was present in the original sample? Answer in units of g.