题干

食用碱的主要成分是Na2CO3(常含有少量的NaCl)。课外探究小组为测定市售食用碱中Na2CO3的含量,设计了如图实验装置:


设计思路:用空气将装置B中生成的二氧化碳缓缓吹入装置D中,利用装置D的质量变化测定食用碱中Na2CO3的含量.请结合实验装置和设计思路,回答下面问题:

①装置E的作用是____

②缓缓通入空气的目的是____

③若撤除装置A,直接通入空气会导致实验结果____(填“偏大”、“偏小”或“不变”)。

上一题 下一题 0.0难度 选择题 更新时间:2015-11-10 04:21:21

答案(点此获取答案解析)

吸收空气中的水蒸气、二氧化碳,防止进入装置D中,使氢氧化钡和二氧化碳完全反应,偏大

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    People who are confident really seem to be naturally outstanding and just seem to do everything with more styles than others.____ It is a habit that everyone can develop in life. Try these simple tips to drill and build up your confidence:

1)Admit your shortcomings calmly.

    Do not try to flee from them or cover them. Face them bravely.____ Fight against them every day until the day when you could break away and conquer them.

2)Dress for self-confidence.

    ____ And therefore pay attention to your dress, display your unique physical advantages and exhibit your best image. In addition, on formal occasions such as a business conference or a wedding ceremony, elegant dressing contributes to building your confidence.

3)____

    You should break your routine that deals with the work passively. Concentrate your efforts immediately on overcoming it, because it will make your restless mind at ease and build your self-confidence.

4)Be positive.

    Feel pity neither on yourself nor on others. If you are used to hating and accusing yourself, others would tend to do that and believe it. Instead, you should speak positively about yourself, your progress, and your bright future.____

A. Don't judge a person by appearance.

B. Build your confident vocabulary.

C. Don't put off what you eventually have to do.

D. Actually, true self-confidence is neither born nor acquired overnight.

E. By doing so, you would encourage your growth in a positive direction.

F. Then talk about them to a reliable mate, a friend or a family member.

G. Your appearance could put you into embarrassment or increase your confidence.