题干

小明对于蜡烛燃烧过程进行了一系列的探究,下列说法正确的是(  )

 

A:点燃蜡烛后,电子秤示数逐渐减小(如图所示),蜡烛减小的质量等于燃烧后生成物的总质量

B:在燃烧的蜡烛上方罩上干冷烧杯,看到有水雾生成,说明蜡烛中一定含有氢氧两种元素

C:将大烧杯罩在燃烧蜡烛中,一会儿,蜡烛熄灭,说明蜡烛燃烧生成二氧化碳

D:已知蜡烛的主要成分CxHy燃烧的方程式是CxHy+33O2 点燃__ 25CO2+16H2O,则物质的化学式是C25H32

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答案(点此获取答案解析)

D

同类题2

根据短文内容, 从短文后的选项中选出能填入空白处的最佳选项。选项中有两项为多余选项。

    Are you satisfied with your life? How often do you think of reasons why everyone around you is successful though they are not usually better than you? What do you do wrong? Here are some things you should stop doing to be successful.

1) ____

    Different people may interpret “success” in different ways: some of them measure it in money, other ones — in positive changes to people around them and the world.____ And do not worry about what other people think, and come after what makes you happy.

2)Do not believe anything without questioning it.

    ____ They are critical thinkers, and they understand that we are all ruled by our prejudices; so, they will always question new information.

3)Do not worry about all unpredictable things that may happen to you.

    If you want to be successful, stop thinking about everything that MAY happen to you.____ Be ready to change your deeds and decisions when things suddenly don't go according to your plan.

4)Do not care about what other people think of you.

    ____ Your attempts to become “good” for everyone will turn into nothing but new worries, stresses, and problems. Successful people do not concentrate on quantity of people to please, but worry about their quality and focus on developing friendships with people they really care about.

Success is good, but you should understand that life will get depressing without friendship and love.

A. Try to feel comfortable with the reality and accept the fact your future can't be predicted.

B. Do not let others decide what “success” is for you.

C. As far as we all know, it's impossible to please all the people who surround us.

D. Do not wait for the “right time” to do anything.

E. Successful people never ignore or avoid problems, no matter how big and awful they seem.

F. Successful people do not just accept any new information to be true.

G. If you want to be successful, do not let others force their interpretation of success on you.