问题 选择题

今有共平面的一种大环轮烯:[18]轮烯。如下图所示,有关它的说法不正确的是(    )

A.[18]烯的分子式为C18H18

B.1 mol [18]轮烯最多可与9 mol氢气发生加成反应生成环烷烃

C.[18]轮烯与苯互为同系物

D.[18]轮烯燃烧时会产生浓的黑烟

答案

答案:C

[18]轮烯中18个碳原子,9个双键,一个环,故氢原子个数为18×2+2-10×2=18,即分子式为C18H18,因有9个双键,故最多可与9 mol H2加成,因含碳量高,故燃烧会产生浓烟。结构无苯环,不可能与苯互为同系物。

选择题
阅读理解

B

As an effect of the high fuel prices spent on bus transportation, some American schools are changing to a four-day week. That means longer days instead of the traditional Monday through Friday schedule.

Having been approved for three years and beginning in the fall, students in the Maccray school district in Minnesota will be in school from Tuesday to Friday. Each school day will be 65 minutes longer. Officials say the district expects to save about sixty-five thousand dollars a year in transportation costs.

In new Mexico, the first school district changed to a four-day week in 1974 because of the Arab oil boycott(抵制). Now, 17 out of 89 districts use it.

In Custer, South Dakota, students have been going to school four days a week since 1995. Superintendent Tim Creal says the change has saved about one million dollars over just the past eight years. He sees other benefits, too. Students get more instructional time, and activities that used to take up class time are now held on non-school days. He says that in the future, the growth of online classes could make it possible to require even fewer days in school. High fuel prices are driving college students to take more online classes.

A four-day school week sounds like a great idea for students and teachers, but working parents may have to pay for child care for that fifth day.

小题1:According to Tim Creal, what makes it possible to have even fewer days in school?

A.The increasing number of private tutors.(私人教师)

B.The development of teaching methods.

C.The increase in the number of online classes.

D.The growth in the income of Americans.小题2: It can be learned from the passage that______

A.students will be in school from Monday to Tuesday.

B.four-day week was first carried out in South Dakota.

C.Maccray will save one million dollars every year.

D.Minnesota state has approved the four-day week plan小题3:The passage is mainly about______

A.some school’s four-day week plan

B.districts using a four-day week.

C.how to save on transportation fees.

D.expense of school transportation.