在有关离子方程式的书写及正误判断的专题复习中,我们发现学生对涉及反应物“量多量少”而导致离子反应不同的离子反应方程式的判断和书写这类问题总是含糊不清,错误率极高,而此类题目却又几乎是每年高考中必考题目.那么应如何突破此难点,让学生明确什么时候需要考虑反应物的“量多量少”呢?我们整理出了如下几类情况,供大家参考.一、多元弱酸或其对应的酸酐与碱反应时,必须考虑反应物“量多量少”对反应的影响1.例题分析 In a review of the writing of the ion equation and its positive and negative judgments, we found that students were always vaguely aware of the judgments and writing of ionic reaction equations that involved different ion reactions involving reactants. , The error rate is extremely high, but such topics but almost every year the entrance exam will test the problem .How should we break through this difficulty, so that students need to be clear when reactants “quantity of less ”? Out of the following types of situations for your reference.A multi-weak acid or its corresponding anhydride and alkali reaction, you must consider the reactant “a large amount of less” impact on the reaction 1.Examples of analysis