Final answer:
The mass of magnesium is 0.35 g, the mass of magnesium oxide is 0.81 g, and the mass of oxygen is 0.46 g. These values are obtained by subtracting the masses of the crucible with lid from the masses with magnesium and with magnesium oxide, respectively.
Step-by-step explanation:
The question requires a calculation of the mass of magnesium (Mg), magnesium oxide (MgO), and oxygen (O) based on the given masses of a crucible with lid alone, with magnesium, and with magnesium oxide. To find the mass of magnesium used, we subtract the mass of the empty crucible with lid from the mass of the crucible with lid and magnesium: 30.99 g - 30.64 g = 0.35 g. To find the mass of magnesium oxide, we subtract the mass of the empty crucible with lid from the mass with magnesium oxide: 31.45 g - 30.64 g = 0.81 g. Lastly, to find the mass of the oxygen that reacted with magnesium, we subtract the mass of magnesium from the mass of magnesium oxide: 0.81 g - 0.35 g = 0.46 g. This shows the amounts of Mg, MgO, and O present.