趁热过滤和冷却结晶有什么区别

趁热过滤和冷却结晶有什么区别
2025-02-15 21:41:47
推荐回答(2个)
回答1:

趁热过滤,说白了,就是过滤。为了防止晶体析出,尽可能的获得溶液,所以趁热过滤。

冷却析出,就是冷却热饱和溶液,使得晶体析出。

回答2:

趁热过滤一般用于有两种(或多种)溶质的溶液提纯,既然是提纯,那就一定有目标物质,这种目标物质必须具备溶解度受温度影响较大的特点。而其他物质受温度影响不大,且溶解度较低或较大
例如:NaCl和KNO3混合溶液提纯KNO3,就是趁热过滤的典型例子:
首先是将NaCl和KNO3溶液加热蒸发,由于NaCl在温度较高的条件下溶解度升高不多,但溶剂(水)变少,NaCl析出,这时我们将溶液进行过滤,就可以得到含较少NaCl的KNO3溶液
过滤后的溶液在烧杯中会降温,这时可以加点水,以保证【冷却结晶】后的KNO3比较纯净

冷却结晶的原理是KNO3在温度降低的时候,溶解度降低,析出溶液,而NaCl溶解度几乎不受影响,所以NaCl不析出,但为了保证NaCl不析出,可以加点水,即加大溶剂(可能会牺牲一点KNO3)

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