最近，科学家研究确认，一些油炸食品含有致癌物质丙烯酰胺（C3H5ON）。回答并计算（不要求写计算过程）：
（1）丙烯酰胺由 种元素组成，1个丙烯酰胺分子由 个原子构成；
（2）丙烯酰胺中碳、氢、氧、氮四种元素的质量比为 ；
（3）丙烯酰胺中碳元素的质量分数为 。（结果保留至0．1%）
（1）4、10；（2）36：5：16：14；（3）50．7% 。
题目分析：（1）由丙烯酰胺（C3H5ON）可知：丙烯酰胺由碳、氢、氧、氮四种元素组成；1个丙烯酰胺分子由3+5+1+1=10个原子构成；（2）根据化合物中各元素质量比= 各原子的相对原子质量×原子个数之比。丙烯酰胺中碳元素、氢元素、氧元素、氮元素的质量比=（123）：（1×5）：16：14=36：5：16：14 。（3）根据化合物中元素的质量分数=
，进行分析解答。丙烯酰胺（C3H5ON）中碳元素的质量分数=
≈50．7%
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| Most adults（成年人） once studied at school,had classes and did their homework every day. The same 1 is going on at school now. 2 it seems that doing weekend homework is 3 problem for the modern students. All the students should agree that weekend homework should be abolished（取消）.It’s 4 for them studying at school five days a week.They have a lot of interests.With homework to do on Saturday and Sunday,how can they find 5 to help around the house,go and watch a football or basketball game or a good film,join in family recreations（娱乐）,or just have 6 at home?Because of these or other activities,the homework can’t be finished until 7 .So their weekend homework is usually done in such a hurry that on Monday teachers are 8 and often threaten（威胁） to fail whole class of students because they know nothing about the 9 .If there were no weekend homework against the students’ wishes,they would be happy to go to school on Monday 10 having a good rest and learn what the teachers teach. | |||
| ( )1.A.thing ( )2.A.Also ( )3.A.no ( )4.A.not enough ( )5.A.friends ( )6.A.a rest ( )7.A.Monday afternoon ( )8.A.pleased ( )9.A.lesson ( )10.A.until | B.school B.But B.another B.enough B.time B.an exam B.Saturday afternoon) B.sorry B.games B.when | C.class C.Still C.one C.no good C.places C.a lesson C.Friday night C.unhappy C.interests C.before | D.homework D.Though D.other D.no use D.money D.a picnic D.Sunday night D.not worried D.activities D.after |