举例说明什么是化学腐蚀?___________________________________________________________________ 答案:金属跟接触到的物质(如O2、Cl2、SO2等)直接发生化学反应而引起的腐蚀叫做化学腐蚀。 例:Mg、Al在空气中被氧气氧化而腐蚀:Mg+O2MgO 4Al+3O22Al2O3,Fe与Cl2直接反应而被腐蚀:2Fe+3Cl22FeCl3。() 6. — have you studied in this middle school? —Since two years . A. How long;before B. How much time;before C. How soon;ago D. How long;ago