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一、稀溶液冷却时,溶质不和冰一起析出而只析出冰的原因溶液冷却时析出的固态物质,可能是冰,也可能是溶质,或冰和溶质一起析出,这应由溶液的浓度决定。下面以(NH4)2SO4水溶液为例予以说明。表1是(NH4)2SO4水溶液在不同浓度下的凝固点。表2是(NH4)2SO4在不同温度下的溶解度。如果用这两个表的数据作图,可得到图1,常称之为相图。图中LA线是(NH4)2SO4溶液的冰点下降曲线,AN是(NH4)2SO4溶解度曲线(AN线不能无限延长,N点是饱和溶液的沸点,为108.9℃)。LA和AN曲线以上的区域(区域Ⅰ)
First, the dilute solution cooling, the solute is not precipitated with ice and only precipitated ice The solid solution precipitated when the material may be ice, it may be solute, or ice and solute precipitation, which should be determined by the concentration of the solution . The following (NH4) 2SO4 aqueous solution as an example to illustrate. Table 1 is (NH4) 2SO4 aqueous solution at different concentrations of freezing point. Table 2 shows the solubility of (NH4) 2SO4 at different temperatures. If you use these two tables of data mapping, you can get Figure 1, often called the phase diagram. The LA line is the freezing point declining curve of (NH4) 2SO4 solution. AN is the solubility curve of (NH4) 2SO4 (the AN line can not be extended indefinitely, and the N point is the boiling point of the saturated solution at 108.9 ° C). The area above the LA and AN curves (Area I)