在－50℃液氨中有2NH3(液) 
NH4++NH2—的电离平衡关系，两离子的平衡浓度均为1×10—15mol/L，下列对－50℃时液氨的离子积表达正确的是
A．离子积是1.0×10—30
B．离子积是1.0×10—15
C．若液氨中加入NaNH2，其离子积增大
D．若液氨中加入NH4Cl，则[NH4+]增大，离子积数值增加
答案：A
题目分析：液氨中的离子积为c(NH4+) c(NH2-)=1×10-15×1×10-15=1.0×10-30，A项正确，B项错误，离子积只与温度有关，与浓度无关，所以C、D错误。答案选A。
点评：离子积是温度的函数，当温度改变离子积改变，浓度和压强改变离子积不变。
第五部分: 任务型阅读（共10小题；每小题1分，满分10分） 请认真阅读下列短文，并根据所读内容在文章后表格中的空格里填入一个最恰当的单词。注意：每个空格只填1个单词。请将答案写在答题卡上相应题号的横线上。 Celebrating sleep World Sleep Day, observed on 21 March, was created to bring attention to the growing number of sleep problems worldwide. Sleep is a natural part of human life, but many people in the modern world ignore its importance. As a result, sleep problems are increasingly common. In 2002, scientists at the University of Athens in Greece conducted a survey of over 35,000 people in 10 countries around the world, including China, Belgium and South Africa. Of the people that responded to the survey, 24 percent said that they did not sleep well, and based on their responses, 31.6 percent were diagnosed(诊断) with insomnia(失眠) and another 17.5 percent were diagnosed with borderline insomnia. In addition, 30.7 percent of survey respondents reported visiting a doctor for help with sleep problems and 11.6 per cent said that they felt very sleepy during the day. Overall, the survey found that many people suffer the effects of poor quality sleep, some examples of which are being unable to fall asleep and waking up in the middle of the night. The main factors causing these problems are pressure from school or work and a fast pace of life, but noise pollution and light pollution also interfere with sleep and contribute to poor quality sleep. The survey’s findings are particularly troubling because large numbers of people were found to have difficulty sleeping at night. The short-term effects of this are tiredness and trouble concentrating. If this happens for a long time, the risk of gaining weight and having a heart attack may increase. There are many things you can do to improve the quality of your sleep. First, you should have regular sleep habits. Try to go to bed and wake up around the same time each day. You also need to make your bedroom a cool, dark, quiet place to sleep so that heat, light and noise do not disturb you. At night, you should also avoid things that contain caffeine, such as chocolate, coffee, tea and many soft drinks, as caffeine may keep you from sleeping. Getting a good night’s sleep is important for everyone. By following the advice above, you can rest better at night and work better during the day. Title: Celebrating Sleep
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