除去物质中所含杂质使之变成纯净物的问题是中考中常见的题型。解这类题,必须熟知各物质的物理性质、化学性质,对具体问题进行具体分析,选择恰当的试剂和操作方法。做到既除掉杂质又符合除杂的要求。 除杂时,要符合下列要求:不能引入新的杂质;不能减少被提纯物;杂质与被提纯物容易分离;要把被提纯物恢复到原来的状态。 除杂的方法有物理方法和化学方法。物理方法一 The problem of removing the impurities contained in the substance to make it pure is a common question in the examination. To solve such problems, you must be familiar with the physical and chemical properties of each substance, conduct specific analysis of specific problems, and select the appropriate reagents and methods of operation. Do away with impurities and meet impurity removal requirements. When removing impurities, the following requirements must be met: no new impurities can be introduced; the purified material cannot be reduced; the impurities and the purified material are easily separated; and the purified material is restored to its original state. There are physical methods and chemical methods for removing impurities. Physical method one