Jawabanmu

2014-06-17T23:58:19+07:00
Fe3O4 ⇒ 3 Fe + 2 O2
mol Fe3O4 =gr/Mr = 200/232 = 0,86 
mol Fe = 3/1 x 0,86 = 2,58 mol 
mol = gr/mr
2,58 x 56 = gr Fe
144,5 gram = gr Fe

Persentase = (84/144,5) x 100% = 58 %