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加强一题多解的训练,可以帮助学生多角度思考问题,丰富学生的解题思路,锻炼学生思维的敏捷性,这对提高学生的思维能力和解题能力是大有裨益的。本文以1997年全国初中化学奥林匹克竞赛河南省赛区预赛第48题述之。 题目 碳酸钙和钙的混合物在空气中煅烧,反应完全后,与煅烧前质量相等。问混合物中碳酸钙的质量分数是多少? 这是一道无数据计算题,也是启迪学生思维的好题。 思路分析:题给的条件中,加热前后固体总质量相等,指的是加热后所得氧化钙的总质量
Strengthening the training of multiple solutions can help students think in multiple ways, enrich students’ problem-solving ideas, and train students’ agility in thinking. This is of great benefit to improving students’ ability to think and solve problems. This article is based on the 48th title of the preliminaries of the 1997 Henan Provincial Junior High School Chemistry Olympiad. Title The mixture of calcium carbonate and calcium is calcined in air. After the reaction is complete, it is equal to the mass before calcination. What is the mass fraction of calcium carbonate in the mixture? This is a no-data calculation problem, and it is also a good question for enlightening students’ thinking. Analysis of ideas: In the given conditions, the total solid mass before and after heating is equal, referring to the total mass of calcium oxide obtained after heating.