化学选择题具有知识覆盖面广,文字迷惑性强,题中隐含因素多,各类型的解法杂等特点。在解题过程中,抓住关键,找出隐含。例1.有Na_2CO_3,NaHCO_3、CaO和NaOH组成的混合物27.2g,把它们溶于足量的水中充分反应后,溶液中Ca~(2+),CO_3~(2-),HCO_3~-均转化为沉淀,经蒸干最后得到白色固体共29g,原混合物中Na_2CO_3的质量是 (A)10.6g (B)5.3g (C)5.9g (D)无法确定解析:此题关键就是HCO_3~-的转化,隐含 Chemical multiple-choice questions have the characteristics of wide coverage of knowledge, strong confusing characters, many hidden factors in the questions, and various types of solutions. In the process of solving the problem, grab the key and find out the implications. Example 1. There are 27.2 g of a mixture of Na 2 CO 3 , NaHCO 3 , CaO and NaOH. When they are fully dissolved in a sufficient amount of water, Ca 2+, CO 3 2-, and HCO 3 - are all converted. To precipitate, after evaporation to give a white solid, a total of 29g was obtained. The mass of Na 2 CO 3 in the original mixture was (A) 10.6g (B) 5.3g (C) 5.9g (D) Unsure to resolve: The key to this question is HCO_3~- Conversion, implicit