(2) Iron will rust in the presence of oxygen and water, and plating a layer of chromium on its surface can effectively prevent water and oxygen from contacting with iron, thus playing a role in rust prevention;
(3)①II is the reaction between iron oxide and hydrochloric acid, and the equation is: Fe2O3+6HCL = 2FeCl3+3H2O; Because this process is the process of producing iron, ferric chloride and sulfuric acid, it can be seen from the graphic analysis that A should be metallic iron, so the reaction of III can be: 3CO+Fe2O3? High temperature? . ? 2Fe+3co 2；
②a, because I is the reaction of ferrous disulfide and oxygen, the equation is 4FeS2+ 1 1O2? High temperature? . ? 2 fe2o 3+8so 2；
B. The sulfur-containing substances involved in the above process are FeS2, SO3 and SO2, and their valences are-1, +6 and+4 respectively;
C, according to the diagram, the solution of B is ferric chloride and the solution of C is sulfuric acid. The release of iron will lead to the process of Fe+2FeCl3=3FeCl2, and the hydrogen in sulfuric acid will be replaced by iron to generate hydrogen, so the appearance cannot be the same;
D, assuming that there is no loss in the conversion process and the quality of sulfur is the same, then the maximum amount of sulfuric acid that can be produced by 150t pyrite containing 280% FeS is X. 。
ferrous sulfate
120? 196
150t×80%？ x
120 150t×80% = 196 x
x= 196t
So choose bcd.
So the answer is: (1)124; Conducting electricity; (2) Isolated from humid air; (3)①fe2o 3+6h cl = 2 FeCl 3+3H2O； 3CO+Fe2O3？ High temperature? . ? 2Fe+3co 2；
②BCD；