去除粗盐可溶性杂质必须第一步去除硫酸根离子——从盐效应角度分析实验步骤

去除粗盐中可溶性杂质的原理是教学中的一个重点,而实验步骤则是教学中的重中之重.中学教学中通常认为氢氧化钠溶液与氯化钡溶液的添加顺序对实验没有影响,但是由于盐效应,经计算可知添加顺序直接影响硫酸根离子是否能够除净,因此该实验的操作步骤必须第一步去除硫酸根离子,否则硫酸根离子将无法除净.

Sulfate Ion Must be Removed in the First Step to Remove Soluble Impurities in Crude Salt:Analysis From Salt Effect Perspective

The principle of removing soluble impurities in crude salt is a key point in teaching, and the experimental steps are the most important. Traditionally, most teachers thought the sequence for the addition of sodium hydroxide and barium chloride couldn’t affect the result of the experiment. However, according to the calculation, it is found that the sequence will largely affect the removal of sulfate ion because of the salt effect. Therefore, sulfate ion should be removed first in the procedure of this experiment.