Hey there!:
Molar mass :
Fe₂O₃ = 159.69 g/mol
O₂ = 31.99 g/mol
By reaction stochiometry :
4 Fe + 3 O₂ = 2 Fe₂O₃
3 * (31.99 g O₂ ) ------------------ 2 * ( 159.69 ) g Fe₂O₃
8.93 g O₂ --------------------------- ( mass O₂)
mass O₂ = ( 8.93 * 2 * 159.69 ) / ( 3 * 31.99 )
mass O₂ = 2852.0634 / 95.97
mass O₂ = 29.71 g Of Fe₂O₃
Hope this helps!
