Answer:
7.5 mol
Step-by-step explanation:
2Al + 3Br₂ ⟶ 2AlBr₃
You want to convert moles of AlBr₃ to moles of Br₂.
The molar ratio is 3 mol Br₂:2 mol AlBr₃.
Moles of Br₂ = 5 × 3/2
Moles of Br₂ = 7.5 mol Br₂
You need 7.5 mol of Br₂ to produce 5 mol of AlBr₃.