为什么检验硫酸根离子,要用BACL2而不是硝酸钡?

2025-04-06 06:41:04
推荐回答(1个)
回答1:

先往溶液中加足量稀盐酸,直到没有气体产生,然后过滤,往得到的滤液中加入硝酸钡,若产生沉淀,再加入稀硝酸,若沉淀不溶解,则可判定原溶液中存在硫酸根离子.开始加足量稀盐酸是为了除去亚硫酸,因为亚硫酸会被硝酸根离子氧化为硫酸根离子,影响检测.且因为氯离子可能与银离子形成氯化银沉淀,影响检测,因此之后的滤液不能用氯化钡检验,只能用硝酸钡.在初中阶段,可以直接加氯化钡,再加稀硝酸检验(但氯离子可能与溶液中原有的银离子、亚汞离子形成沉淀,当铅离子浓度较高时,也可能形成氯化铅沉淀).但绝对不能用稀盐酸,因为溶液中可能有其他离子能与钡离子形成沉淀,而这些沉淀都溶于稀硝酸.但有些沉淀不溶于稀盐酸,如银盐、亚汞盐和铅盐.

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