下列关于溶液中的描述正确的是
A．常温时，
溶液的
，则该溶液中
B．
溶液与
溶液反应至中性的离子方程式为：
C．常温下物质的量浓度相等的下列四种溶液：①
；②
；③
；④
，四种溶液中
比较：②
①④③
D．常温下
的溶液：
、
、、
可以常量共存
答案：A
A中根据电荷守恒c(H＋)＋c(Na＋)=c(NO2－)+c(OH－)可知,c(Na＋)－c(NO2－)＝c(OH－)－c(H＋)＝10-6mol/L－10-8mol/L＝9.9×10-7mol/L，A正确。B不正确，应该是2H＋＋SO42－＋Ba2＋＋2OH－=BaSO4↓＋2H2O。硫酸氢铵能电离出氢离子，抑制NH4＋水解。同样亚铁离子水解也显酸性，抑制NH4＋水解。醋酸铵中CH3COO－水解显碱性，促进NH4＋水解，溶液中NH4＋浓度从大到小的顺序是①④③②，C不正确。选项D中氢离子浓度是10-4mol/L，即溶液显酸性，能产生硅酸沉淀，D不正确，答案选A。
Soon it would be the holidays, but before that, there were year exams. All the 36 _____ had been working hard for some time, reviewing their lessons for the exams. If they didn’t 37 _____, they would have to retake them in September. There were usually a few who 38 _____, but Jane didn’t want to be one of them. She had worked hard all year, 39 _____ just before the exams she was working so hard that her sister Barbara was 40 _____ about her. She went to bed too 41 _____. The night before the first exam, Barbara 42 ____ that she have an early night and take a 43 ____ pill. She promised to wake 44 _____ up in the morning. As she was falling asleep, Jane was afraid that she might oversleep. Her 45 _____ kept jumping from subject to subject. At last, with the help of 46 ____, she went to sleep. In no time at all, she was sitting in the examination hall, looking at the examination 47 _____, but she couldn’t answer any of the questions. 48 _____ around her was writing pages and pages. 49 _____ she thought hard, she couldn’t find anything to write 50 _____. She kept looking at her 51 _____. Time was running out. There was only an hour to go. She started one question, wrote two sentences, 52 _____ and tried another one. With only half an hour left she wrote another two sentences. By this time she was so worried that she started 53 ____. Her whole body shook. It shook so much that she 54 ____ up. She was still in bed and it had all been a 55 _____ dream. A minute later, Barbara called her name.
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