40 г                                      Х г   FeO       +       2HCl     -gt;      FeCl2      +       H2On = 1 моль                             n = 1 мольMr = 72 г/моль                     Mr = 127 г/мольm = 72 г                                m = 127 г40 г FeO     -    Х г FeCl272 г FeO    -     127 г FeCl2m(FeCl2) = 40 * 127 / 72 = 70,5 г