## General Chemistry: Principles and Modern Applications (10th Edition)

$mass_{O_{2}}$ = 0.268 g
The mass of the products and the mass of the reactants are equal. This is stated in the Law of Conservation of Mass. So $mass_{products}$ = $mass_{reactants}$ $mass_{Mg} + mass_{O_{2}}$ = $mass_{MgO}$ 0.406 + $mass_{O_{2}}$ = 0.674 $mass_{O_{2}}$ = 0.674 - 0.406 $mass_{O_{2}}$ = 0.268 g Rounding to three significant figures gives $mass_{O_{2}}$ = 0.268 g