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在中学化学教学中,关于结晶水合物自溶液中析出量的计算,有一定难度。本人就这问题总结出以下几种计算方法,供参考。 例题:在20℃时,称取白色粉末状硫酸铜20克,放入100克水中,制成硫酸铜溶液,恰好达到饱和。当加热蒸发除去30克水后,再冷至20℃时,求有多少克胆矾(CuSO_4·5H_2O)析出? 这类问题对于学生学完溶解度概念以后是可以计算的,但是不宜用复杂方法。这里先用逐步逼近法求解(求出在该温度下,至少可
In chemistry teaching in middle schools, there is a certain degree of difficulty in the calculation of the amount of precipitation of crystalline hydrates from solution. I summed up the following calculation methods for reference on this issue. Example: At 20°C, 20 grams of white powdered copper sulfate is weighed and placed in 100 grams of water to make a copper sulfate solution that is just saturated. When heated to remove 30 g of water and then cooled to 20°C, how many grams of cholesteryl bismuth (CuSO_4·5H_2O) precipitated? This kind of problem can be calculated after students learn the solubility concept, but it is not appropriate to use complex methods. This is first solved by a stepwise approximation (at least at this temperature,