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Practice 9  Generally, however, modern examinations are, written. (1) The written examination, where all students are tested on the same question, was probably not known until the nineteenth century. Perhaps it came into existence with the great increase

Practice 9  Generally, however, modern examinations are, written. (1) The written examination, where all students are tested on the same question, was probably not known until the nineteenth century.

某学生在实验报告中有以下实验数据:①用托盘天平称取11.7克食盐;②用量筒量取5.26毫升盐酸;③用广泛pH试纸测得溶液的pH值是3.5;④滴定未知浓度的盐酸用去23.10毫升NaOH溶液.你认为数据合理的是(  ).

某学生在实验报告中有以下实验数据:①用托盘天平称取11.7克食盐;②用量筒量取5.26毫升盐酸;③用广泛pH试纸测得溶液的pH值是3.5;④滴定未知浓度的盐酸用去23.10毫升NaOH溶液.你认为数据合理的是(  ).

现有一含杂质的固体BaCl2样品(杂质不溶于水),取12.5g样品放入烧杯中,然后加入39.6g水使其充分溶解,静置后滤去杂质.取10g滤液,加入100gAgNO3溶液,恰好完全反应生成白色沉淀,过滤后得到107.13g溶液,试计算:(计算结果精确到0.1%)  (1)生成白色沉淀多少克;  (2)10g滤液中溶质的质量分数;  (3)样品中BaCl2的质量分数.

现有一含杂质的固体BaCl2样品(杂质不溶于水),取12.5g样品放入烧杯中,然后加入39.6g水使其充分溶解,静置后滤去杂质.取10g滤液,加入100gAgNO3溶液,恰好完全反应生成白色沉淀,过滤后得到107.13g溶液,试计算:(计算结果精确到0.1%)  (1)生成白色沉淀多少克;  (2)10g滤液中溶质的质量分数;  (3)样品中BaCl2的质量分数.