Question

What is the mass of aluminium in 204g of aluminium oxide?

Answer 1

formulae for aluminium oxide =Al₂O₃
mass of aluminium in its one mole of  oxide = 54gm
now totla no. of moles =  [tex] \frac{given mass}{molecular mass } [/tex] =$\frac{204}{102}$ = 2 mole 
so mass of aluminium in 2 mole = 54 ˣ 2 = 108 gm