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分析近年来全国各省市中考的一些试题,发现有些计算型选择题根本不需要计算就能得出答案,下面浅谈几种方法.一、估计法,即是运用有关知识,结合题目特点通过估计而得出答案的一种方法例1向100 g克饱和硫酸铜溶液中加入1.6 g白色硫酸铜粉末此时析出晶体的质量为()A.2.5 g B.1.6 gC.大于2.5 g D.1.6～2.5 g解析:此题缺少温度和溶解度两个条件,无法解答,但仔细分析,可以通过估计求解.因为无论什么条件下,向饱和硫酸铜溶液中加入1.6 g无水硫
Analysis of some provinces and cities in the country in recent years, the examination of some of the questions and found that some computational choice questions do not need to calculate the answer, the following discussion of several methods. First, the estimation method, that is, the use of knowledge, combined with the characteristics of the topic by estimating A solution to the problem Example 1 To 100 g g saturated copper sulfate solution was added 1.6 g white copper sulfate powder The mass of precipitated crystals () A.2.5 g B.1.6 gC. Greater than 2.5 g D.1.6 ~ 2.5 g Analysis: This question lack of temperature and solubility of the two conditions, can not answer, but a careful analysis, can be solved by the estimate, because no matter what the conditions, the saturated solution of copper sulfate was added 1.6 g of anhydrous sulfur