Answer:
1. Determine the mass of magnesium used:
Crucible, lid, and combustion product (MgO) = 31.89 g
m of Mg = m of combustion product - m of crucible and lid
= 31.89 g - 24.42 g
≈ 7.47 g
2. Determine the mass of magnesium oxide formed:
m of MgO = m of combustion product - m of crucible and lid
= 31.89 g - 24.42 g
= 7.47 g
- Same as the mass of magnesium used, as the reaction is assumed to be complete.
3. Determine the mass of oxygen that combined with the magnesium:
Reaction: 2Mg + O2 → 2MgO
Molar mass of Mg is 24.305 g/mol, and the molar mass of O2 is 31.998 g/mol.
n of Mg = m of Mg / M of Mg
= 7.47 g / 24.305 g/mol
≈ 0.307 mol
Since 2 moles of Mg combine with 1 mole of O2,
n of O2 = n of Mg / 2
= 0.307 mol / 2
≈ 0.1535 mol
mass of O2:
m of O2 = n of O2 × M of O2
≈ 0.1535 mol × 31.998 g/mol
≈ 4.91 g
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hope this helps!
