m.pura 640 g
4FeS2 + 11O2 --> 2Fe2O3 + 8SO2
4x120 8x64
=> m.pura = 4x120x640/8x64 = 600 g pirita pura
1200 g pirita impura ......................... 100%
600g pirita pura ............................... p% = 50%
nr.moli = m/M = , M= 64 g/mol
=> nr.moli = 640/64 = 10 moli SO2