(2)① D？ 2 evaporation? (3) Reduce carbon emissions and improve the utilization rate of raw materials.
Analysis: (1)① In order to ensure the smooth progress of the experiment, it is necessary to check the air tightness of the gas-making device;
② Write chemical reaction formula according to reactants, reaction conditions and products;
③ Treating the tail gas from the perspective of environmental protection;
(2)① The water generated by the reaction should be absorbed from C;
② Crystallization can be precipitated by heating, evaporation and crystallization;
③ After improvement, the raw materials can be recycled.
(1)① In order to make the experiment run smoothly, the air tightness of the device should be checked before the experiment. Therefore, the answer is: air tightness inspection;
(2) The chemical equations for reducing Fe 2 O 3 by CO are 3co+Fe2O3 and 2fe+3co2, so the answers are 3co+Fe2O3 and 2fe+3co2;
③CO is toxic, and excessive CO discharged into the air will pollute the air, which requires tail gas treatment. Therefore, the answer is: to prevent air pollution;
(2)①CO is combustible, so it must be pure in this experiment. There may be water vapor in this experiment, so it is necessary to put concentrated sulfuric acid in bottle C to absorb water. So, choose d;
(2) To obtain soda ash solid, evaporation crystallization can be used, so the answer is: evaporation;
③ The recovery of excess CO from D to A can reduce carbon emissions and improve the utilization rate of raw materials, so the answer is: reduce carbon emissions and improve the utilization rate of raw materials.