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若从H2SO4、Na2CO3、Na2SO4、NaCl、NaNO3、Cu（NO3）2、HNO3七种溶液中取出其中的两种，进行混合及有关实验，所观察到的现象记录如下表．试根据各步实验及其现象先进行分步推断，再推断所取的两种溶液的可能组合．

步骤实验操作实验现象分步推断
（1）将取出的2种溶液进行混合混合溶液无色、澄清．

无其它明显现象

混合溶液中肯定不含Cu（NO3）2
（2）用pH试纸测定混合溶液的pH测定结果pH=2混合溶液中肯定不含______
（3）向混合溶液中滴入足量的Ba（NO3）2溶液有白色沉淀出现混合溶液中可能含有______
（4）向（3）中溶液过滤所得的滤液中滴加AgNO3溶液无明显现象混合溶液中肯定不含______
混合溶液的可能组合（写出溶质的化学式）①______和______ 或

②______和______（写出两种组合即可）

答案

（1）相互间能生成沉淀、气体的反应均不行，如H2SO4与Na2CO3或HNO3与Na2CO3它们反应会生成气体，故答案为：H2SO4与Na2CO3或HNO3与Na2CO3．

（2）实验测定pH为2，故溶液显酸性，而题目中显酸性的物质有两种：H2SO4、HNO3，结合实验（1）的结论，不能存在碳酸钠．故答案为：溶液中含有H2SO4或HNO3中的至少一种，不含碳酸钠．

（3）能与硝酸钡反应生成沉淀的物质有：H2SO4、Na2SO4，故答案为：H2SO4和Na2SO4至少含有一种．

（4）加入硝酸银无现象说明溶液中没有与硝酸银反应的物质，题目中能与硝酸银反应的有氯化钠和碳酸钠，而碳酸钠在（2）中已经排除，故答案为：溶液中不含NaCl．

根据各处实验结论可得满足所有情况的组合只有四种，

故答案为：①H2SO4与Na2SO4

②H2SO4与NaNO3

③H2SO4与HNO3

④HNO3与Na2SO4

多选题
理想变压器原线圈接在如图所示的电压上，原副线圈匝数之比为10：1，串在原线圈上的电流表的示数为1A，则以下叙述正确的是（　　）

A．变压器输出功率为200W

B．若n1=100匝，则输出端线圈的磁通量变化率的最大值为2Wb/s

C．副线圈两端的电压表示数20V

D．变压器的输入功率是由发电厂的输出功率决定的
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