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溶解度中有关物质结晶的计算是教材的难点之一,教材中没有这类题目的例题,而在习题中却出现了这类题目,故在讲课或总复习中应该补充,可以从讨论下列问题的思路、解法着手。[例题]在30℃时,把400克硝酸钾饱和溶液蒸发掉50克水,再冷却到10℃。计算:在理论上能析出硝酸钾晶体多少克?(已知:硝酸钾在30℃和10℃时的溶解度分别为46克和21克)[第一种分析法]若先求出在30℃时,将硝酸钾饱和溶液蒸发掉50克水能析出硝酸钾晶体的质量,
The calculation of the crystallization of related substances in solubility is one of the difficulties in textbooks. There are no examples of such topics in textbooks, and such problems appear in the exercises. Therefore, they should be added during lectures or general review. The following questions can be discussed. Ideas and solutions start. [Examples] At 400C, 400 g of a saturated solution of potassium nitrate was evaporated to 50 g of water, and then cooled to 10C. Calculation: How many grams of potassium nitrate crystals can theoretically be precipitated? (Knowledge: The solubility of potassium nitrate is 46 g and 21 g at 30°C and 10°C, respectively) [First Analytical Method] If the first calculation is at 30°C When evaporating 50 g of water from a saturated solution of potassium nitrate, the mass of potassium nitrate crystals can be precipitated.