问题 填空题

(3分)60 ℃时硝酸钾的溶解度是110 g,在100 g水中溶解100 g硝酸钾晶体,该溶液中溶质的质量分数为____________________,当对该溶液分别采取下列措施时,所得溶液中溶质的质量分数为:

(1)加入11g硝酸钾晶体______________________.

(2)倒出一半溶液______________________.

答案

50% (1)52.4% (2)50%

100/(100+100)=50% ,(1)110/210=52.4% (2)倒出一半,浓度不变,还是50%

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     Have you ever felt sick or had a headache during a test? Have you ever been so worried about

something that you can't sleep at night?    1   This worry in your mind can made your body feel bad. You

may feel angry, frustrated, scared, or afraid—which can give you a stomachache or a headache.

         2    Good or normal stress might happen when you're called to answer a question in class or when

you have to give a speech. This kind of stress that can help you to get things better done.    3   

     But bad stress can happen if the stressful feelings keep going over a long time.  You may not feel well

if your parents are fighting, if a family member is sick, if you're having problems at school, or if you're

going through anything else that makes you upset every day.     4    

         5    That means making good decisions about how to spend your time. If you're only dealing with

school stuff and have no time to play, you can get stressed. Make sure you keep yourself in mind: Sleep,

Exercise , Leisure(休闲),and Food. If you take care of yourself and get enough sleep and food, and if

you exercise and leave time for fun stuff, you'll probably be less stressed out!

A. However, there are two different kinds of stress.

B. Can you tell a kind of stress from another one?

C. The best way to keep stress away is to have a balanced life.

D. That kind of stress isn't going to help you, and it can actually make you sick.

E. Since bad stress is harmful for us, you'd better try to change it into good stress.

F. If so, then you know what stress is. Stress is what you feel when you are worried or uncomfortable

about something.

G. For example, you may do a better job on your test if the stress pushes you to prepare well before the

test.