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溶质的质量分数是溶质的质量与溶液的质量之比．可用下式计算: 溶质的质量分数=溶质质量/溶液质量×100％ =溶质质量/溶质质量+溶剂质量×100％但是,在平时实际做题中,并非拿着题就可将数据直接导入,即题中所给的溶质并非都全部溶解,或所溶解的物质并非就是溶质等等．所以,往往还得先要根据题意去找出溶质及其质量,否则,计算错误．请看下面几种情况就与众不同．一、求溶质质量分数时,不可忽视溶质的溶解要受溶解度的限制例1 20 ℃时,把20克硝酸钾晶体投入到 50克水中,充分搅拌,所得溶液中溶质的质量分数是多少?(20℃时,KNO3的溶解度是 31．6克) 解析:在温度、溶剂一定的情况下,溶质的溶解是有限的．20℃时,KNO3的溶解度为 31．6克,即在该温度下,100克水中最多只能溶
The mass fraction of solute is the ratio of the mass of the solute to the mass of the solution. The following formula can be used to calculate: solute mass fraction = solute mass / solution mass × 100% = solute mass / solute mass + solvent mass × 100% However, in the actual practice of the usual questions, the data can be directly imported without holding the question, The solute given in the question is not all dissolved, or the dissolved substance is not a solute and so on. Therefore, it is often necessary to first find out the solute and its quality according to the question. Otherwise, the calculation error. Please look at the following situations. First, find the solute mass fraction, can not ignore the dissolution of the solute subject to the solubility constraints Example 1 20 °C, 20 grams of potassium nitrate crystals into 50 grams of water, fully stirred, the resulting solution in the solute mass fraction? ( The solubility of KNO3 at 20°C is 31.6 g.) Resolution: Under certain conditions of temperature and solvent, the solubility of solute is limited. At 20°C, KNO3 has a solubility of 31.6 g, which means that at this temperature, only 100 g of water dissolves.