(20 12? In order to determine the mass fraction of iron in iron-carbon alloy (regarded as iron-carbon mixture), chemical interest group in Taiyuan No.2 model)

(1) carbon reacts with excess concentrated sulfuric acid to produce carbon dioxide, sulfur dioxide and water. The chemical equation of the reaction is C+2H2SO4 (concentration)? △? . ? CO2↑+2SO2↑+2H2O，

So the answer is: C+2H2SO4 (strong)? △? . ? CO2 ↑+ 2so 2 ↑+ 2H2O；

(2) Close the piston of the separating funnel, connect a conduit behind the E device, then insert the last conduit into the water, heat the gas conduit of the generating device until it bubbles, and stop heating a section of water column to prove that the device is airtight.

So the answer is: insert the airway into the water, heat the flask, the airway bubbles, stop heating, and a section of water column rises;

(3) Weighing the ag Fe-C alloy, adding excessive concentrated sulfuric acid, stopping heating when no gas escapes in A, and taking out the E device for weighing. When e increases bg, the mass of carbon dioxide produced is bg. According to the law of conservation of mass, the mass of carbon in mg iron-carbon alloy is12b44 = 3b11g, and the mass of iron is Ag-. 3b 1 1a× 100%，

So the answer is: 1 1a? 3b 1 1a× 100%；

(4) Device C absorbs sulfur dioxide by using the strong oxidation of potassium permanganate solution, and the ion reaction is 5SO2+2mno4-+2h2o = 5SO4-+2mn2++4h+.

Therefore, the answer is: absorb and remove sulfur dioxide; 5so 2+2mno 4-+2H2O = 5so 42-+2mn 2 ++ 4H+；

(5) The reagent contained in E is alkali lime, which can absorb CO2 and H2O in the air to increase B. The improved method is to add a drying tube filled with alkali lime to prevent CO2 and water from entering the air. The carbon dioxide produced in the device can not be completely absorbed by alkaline lime, which will lead to low determination results.

So the answer is: a drying pipe containing alkali lime is connected behind the E device; The CO2 gas produced by the reaction is not completely discharged into device E, resulting in low B value.