A. Using concentrated sulfuric acid to react with the iron filings, the concentration of sulfuric acid and iron filings to happen the obturation. The reaction stops, so A is wrong;
B. The use of finely ground iron powder reaction, increasing the contact area of the reactants, the reaction rate is accelerated, so B is correct;
C. Control the temperature at 50 to 70 ℃, the temperature is higher, the rate of reaction is fast, the temperature in the ferrous sulphate of the solubility of the largest, conducive to the reaction, so C is correct;
D. Control temperature at 80 to 100 ℃, dilute sulfuric acid at 100 ℃ into a gaseous state, is not conducive to the full reaction of iron and dilute sulfuric acid, in the temperature of ferrous sulfate solubility becomes smaller, is not conducive to the reaction, so the D is wrong;
The answer is: Fe + 2H + = Fe2 + + H2 ↑; B, C;
② A. Concentration of sulfuric acid for the 4Fe2 + + O2 + 4H + ? 2H2O is equal to increase the concentration of reactant hydrogen ions, the equilibrium to generate trivalent iron ions in the direction of the move, so you need to control the concentration of dilute sulfuric acid can not be too high, so the A is correct;
B. Concentrated sulfuric acid density is greater than that of water, concentrated sulfuric acid to prepare the reaction of the dilute sulfuric acid, it should be concentrated sulfuric acid injected into the de-O2 distilled water, otherwise the water into the concentration of sulfuric acid splashing easy to accidents, so the B is wrong;
C. When the reaction to maintain n (Fe)/n (H2SO4) > 1, iron excess, excess iron and trivalent iron ions reaction Fe + 2Fe3 + = 3Fe2 +, can reduce the content of Fe3 + in the product FeSO4, so C is correct;
D. Reaction should be frequently added Fe2 (SO4) 3 stirring, the introduction of trivalent iron ions, increase the content of Fe3 + in the product FeSO4. In the Fe3 + content, so D is wrong;
The answer is: A, C;
③ with iron filings and dilute sulfuric acid reaction to prepare FeSO4, containing insoluble solids in excess of iron, excess iron and solution of ferrous sulfate separation should be filtering operation, and the final filtrate obtained by evaporation and concentration, cooling crystallization, filtration can be obtained FeSO4?7H2O crystals,
Therefore, the answer is: filtration;
(2) ① sulfuric acid to dissolve a small amount of Cu, Al scrap iron filings, the solution contains ferrous ions, copper ions and aluminum ions, according to the relationship between precipitation and PH table can be seen, when the PH is equal to 6.7, the copper ions are all converted to copper hydroxide precipitation, aluminum ions are all converted to aluminum hydroxide precipitation, this time ferrous ions for the precipitation, when the PH is greater than 7.5 When the PH is greater than 7.5, ferrous ions begin to precipitate, so the PH between 6.7 to 7.5,
The answer is: 6.7 to 7.5;
② hydrogen ions and nitrate in the same solution, equivalent to dilute nitric acid, ferrous ions are reductive, acidic solution nitrate ions have strong oxidizing properties, redox reaction occurs, generating nitric oxide and trivalent iron ions, divalent iron ions become Trivalent iron ions lose one electron, nitrate ions get three electrons into nitric oxide, so ferrous ions and trivalent iron ions before the coefficient are 3, and then according to the conservation of atoms, the ionic reaction equation for 3Fe2 + + NO3 - + 4H + = 3Fe3 + + NO ↑ + 2H2O,
The answer is: 3Fe2 + + NO3 - + 4H + = 3Fe3 + + NO↑+2H2O;
③ reaction Ⅱ need strong oxidizing acid will oxidize the divalent iron ions, nitric oxide is toxic, but nitric oxide is easy to react with oxygen to generate nitrogen dioxide, nitrogen dioxide and water reaction to generate nitric acid, the total reaction for the 4NO + 3O2 + 2H2O = 4HNO3, O2 and reaction Ⅱ NO, according to the ratio of 3:4 mixed and re-admittance to reaction Ⅱ, can save Fe (NO), can save Fe (NO), can save Fe (NO). 2 electrons, trivalent iron ions into divalent iron, gained 1 electron, so trivalent iron ions and ferrous sulfide before the coefficient are 2, according to the conservation of atoms, the ionic reaction equation of the reaction is 2Fe3 + + 3S2- = 2FeS ↓ + S,
So the answer is: 2Fe3 + + 3S2- = 2FeS ↓ + S;