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问题 选择题

将铁粉加到一定量的AgNO3、Cu（NO3）2、Zn（NO3）2的混合液中，待充分反应后过滤，向滤渣中加入稀盐酸，没有气体产生，则滤液中（　　）

A．一定没有AgNO3

B．一定没有Cu（NO3）2

C．只有Zn（NO3）2

D．一定有Zn（NO3）2和Fe（NO3）2

答案

因为向滤渣中滴加稀盐酸，没有气泡产生，说明滤渣中没有铁粉，此时反应的情况可能为：①若银和铜全部被置换出来，即滤液没有AgNO3、Cu（NO3）2，此时滤液中只有Zn（NO3）2和Fe（NO3）2；②若银被全部置换出来，而铜没有或是部分被置换出来，此时滤液中含有的溶质为：Cu（NO3）2、Zn（NO3）2和Fe（NO3）2；③若银被部分置换出来，那么此时的铜没有被置换，此时溶液中含有的溶质为：AgNO3、Cu（NO3）2、Zn（NO3）2和Fe（NO3）2；

综合以上三点可以知道无论什么情况，滤液中一定含有的溶质为：Zn（NO3）2和Fe（NO3）2；即选项D是正确的．

故选D．

选择题

下列是生活中常见的现象，只发生了物理变化的是（　　）

A．煤气燃烧

B．水果榨汁

C．食物腐败

D．燃放烟花
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填空题

Stress is our response to threatening or (1) events. We may experience different levels of stress depending on the (2) , meaning the events or circumstances that cause us to feel stress. Stressors can be classified into (3) main categories: (4) events, personal stressors, and (5) stressors. Cataclysmic events are major events that cause stress (6) , immediately, for a great many people at once. Personal stressors are major life events that create stress, including (7) life events. Background stressors are (8) hassles, or minor irritations, or (9) background stressors. Repeated exposure to stressors has both psychological and (10) consequences. The long- term consequence is that body tissues such as the heart and blood vessels can begin to (11) . The (12) system functions less effectively, and (13) our ability to fight off illnesses.
The General Adaptation (14) explains the sequence of physiological reactions to stress. There are three phases to G. A. S. The first is the " alarm and (15) " phase: we respond with alarm, and take (16) to remove the stressor. The second phase is the (17) stage: we fight against the stressor or try to cope with the stressor. This can lead to the third phase. (18) . The exhaustion phase may be an (19) way of trying to avoid the stressors. The body may be telling us that we need to do whatever is (20) to remove the stressor.

Stress is our response to threatening or (1) events. We may experience different levels of stress depending on the (2) , meaning the events or circumstances that cause us to feel stress. Stressors can be classified into (3) main categories: (4) events, personal stressors, and (5) stressors. Cataclysmic events are major events that cause stress (6) , immediately, for a great many people at once. Personal stressors are major life events that create stress, including (7) life events. Background stressors are (8) hassles, or minor irritations, or (9) background stressors. Repeated exposure to stressors has both psychological and (10) consequences. The long- term consequence is that body tissues such as the heart and blood vessels can begin to (11) . The (12) system functions less effectively, and (13) our ability to fight off illnesses.
The General Adaptation (14) explains the sequence of physiological reactions to stress. There are three phases to G. A. S. The first is the " alarm and (15) " phase: we respond with alarm, and take (16) to remove the stressor. The second phase is the (17) stage: we fight against the stressor or try to cope with the stressor. This can lead to the third phase. (18) . The exhaustion phase may be an (19) way of trying to avoid the stressors. The body may be telling us that we need to do whatever is (20) to remove the stressor.
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