2008年北京奥运会“水立方”使用的新科技膜结构为乙烯--四氟乙烯

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问题问答题

2008年北京奥运会“水立方”使用的新科技膜结构为乙烯--四氟乙烯共聚物，其化学式为C₂F₄，请计算：

（1）C₂F₄中碳元素与氟元素的质量比为______．

（2）C₂F₄中氟元素的质量分数为______．

（3）C₂F₄的相对分子质量为______．

答案

（1）由化学式为C₂F₄，则碳元素与氟元素的质量比为12×2：19×4=6：19，故答案为：6：19；

（2）在C₂F₄中，氟元素的质量分数为

19×4

12×2+19×4

×100%=76%，故答案为：76%；

（3）由相对原子质量和化学式，则相对分子质量为12×2+19×4=100，故答案为：100．

句型转换

Rewrite the following sentences as required（根据所给要求，改写下列句子。【1-6】,每空格限填一词。【7】注意大小写) (共14分)

小题1:Jill went on a diet to lose weight last month. (改为否定句)

Jill_________ _________ on a diet to lose weight last month.

小题2:Tom rarely has lunch at home. (改为反意疑问句)

Tom rarely has lunch at home, _________ _________?

小题3:Doris usually does online shopping twice a week. (对划线部分提问）

_________ _________ does Doris usually do online shopping?

小题4:John worked very hard. He managed to find out a solution to the math problem. (两句合并成一句)

John worked _______ hard _______ he managed to find out a solution to the math problem.

小题5:They interviewed the Korean star Lee Minho just now. (改成被动语态)

The Korean star Lee Minho __________ _________ just now.

小题6:“Are you waiting for anybody here?” she asked the man. (保持句意基本不变)

She asked the man _________ he _________ waiting for somebody there.

小题7:is, to come, the first, she, often, to class (连词成句)

___________________________________________________.

判断题

混凝土膨胀剂的限制膨胀率试体养护时，试体之间应保持15mm以上间隔，试体支点距限制钢板两端约30mm。