Answer:
6.8266x10²³ formula units of Fe₃O₄ are needed
Step-by-step explanation:
The reaction of Fe₃O₄ with Al occurs as follows
3Fe₃O₄ + 8Al → 4Al₂O₃ + 9Fe
Where 3 moles of Fe₃O₄ react with 8 moles of Al
To know the number of formula units of Fe3O4 needed for a complete reaction with Al we need to convert the mass of Al to moles in order to find the moles of Fe₃O₄ and the formula units:
Moles Al -Molar mass: 26.98g/mol-:
81.560g Al * (1mol / 26.98g) = 3.0230moles Al
Moles Fe₃O₄:
3.0230moles Al * (3 mol Fe₃O₄ / 8 mol Al) = 1.1336mol Fe₃O₄
Formula units of Fe₃O₄:
1.1336mol Fe₃O₄ * (6.022x10²³ FU / mol) =
6.8266x10²³ formula units of Fe₃O₄ are needed