Answer:
The mass of oxygen that reacted is approximately 1.6 grams of oxygen
Explanation:
The given information are;
The mass of magnesium in the reaction = 2.43 grams
The final mass of the magnesium oxide = 4.12 grams
The chemical equation for the reaction is given as follows;
2Mg + O₂ → 2MgO
From which we see that two moles of magnesium, Mg, reacts with one mole of oxygen gas molecule, O₂, to produce two moles of magnesium oxide, MgO
The number of moles of magnesium present, 
, is given as follows;
By the given chemical equation, 2 moles of magnesium reacts with one mole of O₂, therefore;
1 mole of magnesium will react with 1/2 moles of oxygen which is 0.5 moles of oxygen also;
0.1 mole of magnesium will react with 0.05 moles of oxygen
The mass of one mole of oxygen = The molar mass of oxygen = 32 g/mol
The mass of oxygen in the reaction = The number of moles of oxygen × The molar mass of oxygen
The mass of oxygen in the reaction = 0.05 × 32 = 1.6 grams
Also from the molar mass of MgO which is 40.3044 g/mol, we have;
The mass fraction of oxygen = 16/40.3044 = 0.39698 ≈ 0.4
The mass of oxygen = 0.39698 × 4.12 = 1.636 g
Therefore, the mass of oxygen in the reaction is approximately 1.6 grams.
