Mr(Al2O3) = 27*2 + 16*3 = 102
W(Al) = Ar(Al) * n / Mr(Al2O3) * 100% = 27 *2 / 102 *100% = 53%
W(O) = Ar(O) * n / Mr(Al2O3) *100% = 16 *3 / 102 * 100% = 47%
Mr(Al2O3) = 27*2 + 16*3 = 102
W(Al) = Ar(Al) * n / Mr(Al2O3) * 100% = 27 *2 / 102 *100% = 53%
W(O) = Ar(O) * n / Mr(Al2O3) *100% = 16 *3 / 102 * 100% = 47%