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【简答题】
(6分)对一份稀溶液作初步分析发现，溶液无色、澄清，其中可能含有SO 4 2— 、Na + 、CO 3 2— 、H + 、Cl — 等离子中的若干种。然后又做了如下实验，以确认这些离子是否大量存在。 （1）用pH试纸测溶液的pH值，试纸显红色； （2）取 2mL上述溶液，加入足量硝酸钡溶液，结果生成了不溶于稀硝酸的白色沉淀； （3）取（2）中的上层清液，加入硝酸银溶液，结果又生成了不溶于稀硝酸的白色沉淀。 问：上述实验可以确定溶液中一定含有 离子，一定没有 离子。 设计实验方案检验不能确定的其他离子。 _____ ____________________________________________________________________ _________________________________________________________________________
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