Answer:
172 g Al
Step-by-step explanation:
We know we will need a balanced equation with masses and molar masses, so let’s gather all the information in one place. Â
M_r: Â 26.98 Â Â Â Â Â Â Â Â 101.96
      4Al + 3O₂ ⟶ 2Al₂O₃
m/g: Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â 325
(a) Calculate the moles of Al₂O₃
n = 325 g Al₂O₃ × 1 mol Al₂O₃ /39.10 g Al₂O₃
n = 3.188 mol Al₂O₃
(b) Calculate the moles of Al
The molar ratio is (4 mol Al/2 mol Al₂O₃)
n = 3.188 mol Al₂O₃ × (4 mol Al/2 mol Al₂O₃)
n = 6.375 mol Al
(c) Calculate the mass of Al
m = 6.375 mol Al × (26.98 g Al/1 mol Al)
m = 172 g Al
Note: The answer can have only three significant figures because that is all you gave for the mass of Al₂O₃.
