The Chemical Interest Group used the following devices to explore the principle of ironmaking (1). Before heating Fe2O3, it is necessary to introduce CO for a period of time for the purpose of _ _ _ _

The Chemical Interest Group used the following devices to explore the principle of ironmaking (1). Before heating Fe2O3, it is necessary to introduce CO for a period of time for the purpose of _ _ _ _ _ _. (2) heat the glass tube a. (1) Carbon monoxide is flammable. If mixed with air, it is easy to explode at high temperature or in case of open flame, so carbon monoxide should be introduced first, and the air in the glass tube should be exhausted before heating.

(2) The reaction at A is the reaction of carbon monoxide and ferroferric oxide, which produces iron and carbon dioxide. The chemical equation of this reaction is: Fe3O4+4CO? High temperature? . ? 3Fe+4co 2； The iron refined by this method is pure and contains no carbon;

(3) The generated carbon dioxide can make the clarified limewater turbid, so it can be observed that bubbles are generated in B and the solution becomes turbid; The chemical equation of this reaction is: CO2+Ca (OH) 2 ═ CaCO3 ↓+H2O;

(4) Carbon monoxide is toxic, and direct discharge into the air will cause air pollution. So add an alcohol lamp at C to ignite carbon monoxide. The chemical equation of this reaction is: 2CO+O2? Light it? . ? 2CO2。

So the answer is: (1) exhaust the air in the glass tube to prevent explosion when heating;

(2)Fe3O4+4CO？ High temperature? . ? 3Fe+4co 2； The iron refined by this method is pure and contains no carbon;

(3) clarify that limewater becomes turbid; co2+ca(oh)2═caco3↓+h2o；

(4) Carbon monoxide is toxic to prevent air pollution; 2CO+O2？ Light it? . ? 2CO2。